SCHEDULE 13G

Amendment No. 0
Echo Bay Mines Limited
Common Stock
Cusip #278751102


Cusip #278751102
Item 1:	Reporting Person - FMR Corp.
Item 4:	Commonwealth of Massachusetts
Item 5:	112,700
Item 6:	0
Item 7:	55,847,090
Item 8:	0
Item 9:	55,847,090
Item 11:	10.223%
Item 12:	    HC


Cusip #278751102
Item 1:	Reporting Person - Edward C. Johnson 3d
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	55,847,090
Item 8:	0
Item 9:	55,847,090
Item 11:	10.223%
Item 12:	IN


Cusip #278751102
Item 1:	Reporting Person - Abigail P. Johnson
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	55,847,090
Item 8:	0
Item 9:	55,847,090
Item 11:	10.223%
Item 12:	    IN



	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)




Item 1(a).	Name of Issuer:

		Echo Bay Mines Limited

Item 1(b).	Name of Issuer's Principal Executive Offices:

		10180-101 Street, Suite 1210
		Edmonton, Alberta  T5J 3S4

Item 2(a).	Name of Person Filing:

		FMR Corp.

Item 2(b).	Address or Principal Business Office or, if None,
Residence:

		82 Devonshire Street, Boston,
Massachusetts  02109

Item 2(c).	Citizenship:

		Not applicable

Item 2(d).	Title of Class of Securities:

		Common Stock

Item 2(e).	CUSIP Number:

		278751102

Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b)
and the person filing, FMR Corp., is a parent holding company
in accordance with Section 240.13d-1(b)(ii)(G).  (Note:  See
Item 7).

Item 4.	Ownership

	(a)	Amount Beneficially Owned:	55,847,090

	(b)	Percent of Class:	10.223%

	(c)	Number of shares as to which such
person has:

	(i)	sole power to vote or to direct
the vote:	112,700

	(ii)	shared power to vote or to
direct the vote:	0

	(iii)	sole power to dispose or to
direct the disposition of:	55,847,090

	(iv)	shared power to dispose or to
direct the disposition of:	0



Item 5.	Ownership of Five Percent or Less of a Class.

	Not applicable.

Item 6.	Ownership of More than Five Percent on Behalf of Another
Person.

	Various persons have the right to receive or the power to
direct the receipt of dividends from, or the proceeds from the
sale of, the Common Stock of Echo Bay Mines Limited.  No
one person's interest in the Common Stock of Echo Bay Mines
Limited is more than five percent of the total outstanding
Common Stock.

Item 7.	Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on By the Parent
Holding Company.

	See attached Exhibit(s) A, B.

Item 8.	Identification and Classification of Members of
the Group.

	Not Applicable. See attached Exhibit A.

Item 9.	Notice of Dissolution of Group.

	Not applicable.

Item 10.	Certification.

	By signing below I certify that, to the best of my knowledge
and belief, the securities referred to above were acquired in the
ordinary course of business and were not acquired for the
purpose of and do not have the effect of changing or
influencing the control of the issuer of such securities and
were not acquired in connection with or as a participant in any
transaction having such purpose or effect.

Signature

	After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this Schedule
13G in connection with FMR Corp.'s beneficial ownership of
the Common Stock of Echo Bay Mines Limited at July 31,
2002 is true, complete and correct.

August 12, 2002
Date

/s/ Stuart Fross
Signature

Stuart Fross
Duly authorized under Power of Attorney
dated July 30, 2002.



	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



	Pursuant to the instructions in Item 7 of Schedule
13G, Fidelity Management & Research Company
("Fidelity"), 82 Devonshire Street, Boston, Massachusetts
02109, a wholly-owned subsidiary of FMR Corp. and an
investment adviser registered under Section 203 of the
Investment Advisers Act of 1940, is the beneficial owner of
55,734,390 shares or 10.203% of the Common Stock
outstanding of Echo Bay Mines Limited  ("the Company") as
a result of acting as investment adviser to various investment
companies registered under Section 8 of the Investment
Company Act of 1940. The number of shares of Common
Stock of Echo Bay Mines Limited owned by the investment
companies at July 31, 2002 included 5,000,000 shares of
Common Stock resulting from the assumed conversion of
5,000,000 shares of ECHO BAY MINES WT 11/14/03 (1
shares of Common Stock for each share of Convertible
Preferred Stock).

	Edward C. Johnson 3d, FMR Corp., through its
control of Fidelity, and the funds each has sole power to
dispose of the 55,734,390 shares owned by the Funds.

	Neither FMR Corp. nor Edward C. Johnson 3d,
Chairman of FMR Corp., has the sole power to vote or direct
the voting of the shares owned directly by the Fidelity Funds,
which power resides with the Funds' Boards of Trustees.
Fidelity carries out the voting of the shares under written
guidelines established by the Funds' Boards of Trustees.

	Fidelity Management Trust Company, 82 Devonshire
Street, Boston, Massachusetts 02109, a wholly-owned
subsidiary of FMR Corp. and a bank as defined in Section
3(a)(6) of the Securities Exchange Act of 1934, is the
beneficial owner of  112,700 shares or 0.021% of the
Common Stock outstanding of the Company as a result of its
serving as investment manager of the institutional account(s).

	Edward C. Johnson 3d and FMR Corp., through its
control of Fidelity Management Trust Company, each has
sole dispositive power over 112,700 shares and sole power to
vote or to direct the voting of 112,700 shares of Common
Stock owned by the institutional account(s) as reported
above.

	Members of the Edward C. Johnson 3d family are the
predominant owners of Class B shares of common stock of
FMR Corp., representing approximately 49% of the voting
power of FMR Corp.  Mr. Johnson 3d owns 12.0% and
Abigail Johnson owns 24.5% of the aggregate outstanding
voting stock of FMR Corp.  Mr. Johnson 3d is Chairman of
FMR Corp. and Abigail P. Johnson is a Director of FMR
Corp.  The Johnson family group and all other Class B
shareholders have entered into a shareholders' voting
agreement under which all Class B shares will be voted in
accordance with the majority vote of Class B shares.
Accordingly, through their ownership of voting common
stock and the execution of the shareholders' voting
agreement, members of the Johnson family may be deemed,
under the Investment Company Act of 1940, to form a
controlling group with respect to FMR Corp.




	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)
	RULE 13d-1(f)(1)  AGREEMENT

	The undersigned persons, on August 12, 2002, agree
and consent to the joint filing on their behalf of this Schedule
13G in connection with their beneficial ownership of the
Common Stock of Echo Bay Mines Limited at July 31, 2002.

	FMR Corp.

	By /s/ Stuart Fross
	Stuart Fross
	Duly authorized under Power of Attorney
	dated July 30, 2002.



	Edward C. Johnson 3d

	By /s/ Stuart Fross
	Stuart Fross
	Duly authorized under Power of Attorney
	dated July 30, 2002.


	Abigail P. Johnson

	By /s/ Stuart Fross
	Stuart Fross
	Duly authorized under Power of Attorney
	dated July 30, 2002.


	Fidelity Management & Research Company

	By /s/ Stuart Fross
	Stuart Fross
	Duly authorized under Power of Attorney
	dated July 30, 2002.