SCHEDULE 13G

Amendment No. 1
Geon Company
common stock
Cusip # 37246W105

Cusip # 37246W105
Item 1:	Reporting Person - FMR Corp.
Item 4:	Commonwealth of Massachusetts
Item 5:	12,300
Item 6:	0
Item 7:	3,036,300
Item 8:	0
Item 9:	3,036,300
Item 11:	12.806%
Item 12:	    HC

Cusip # 37246W105
Item 1:	Reporting Person - Edward C. Johnson 3d
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	3,036,300
Item 8:	0
Item 9:	3,036,300
Item 11:	12.806%
Item 12:	IN

Cusip # 37246W105
Item 1:	Reporting Person - Abigail P. Johnson
Item 4:	United States of America
Item 5:	None
Item 6:	None
Item 7:	3,036,300
Item 8:	None
Item 9:	3,036,300
Item 11:	12.806%
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:

		Geon Company

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

		One Geon Center,
		Avon Lake, OH  44012

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:

		37246W105

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:	3,036,300

	(b)	Percent of Class:	12.806%

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

	(i)	sole power to vote or to direct the vote:	12,300

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

	(iii)	sole power to dispose or to direct the disposition of:
	3,036,300

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



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

	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 Geon Company.  The interest of one person, Fidelity
Value Fund, an investment company registered under the Investment
Company Act of 1940, in the common stock of Geon Company, amounted to
1,460,500 shares or 6.160% of the total outstanding common stock at
December 31, 1999.

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 Geon Company at December 31, 1999 is true, complete and correct.

	February 14, 2000
Date


	/s/Eric D. Roiter
Signature


	Eric D. Roiter
	Duly authorized under Power of Attorney
	dated December 30, 1997, by and on behalf
	of FMR Corp. and its direct and indirect
	subsidiaries


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 2,806,200 shares or
11.836% of the common stock outstanding of Geon Company  ("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 ownership of one investment company, Fidelity Value Fund,
amounted to 1,460,500 shares or 6.160% of the common stock outstanding.
Fidelity Value Fund has its principal business office at 82 Devonshire
Street, Boston, Massachusetts 02109.

	Edward C. Johnson 3d, FMR Corp., through its control of Fidelity,
and the funds each has sole power to dispose of the 2,806,200 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  230,100 shares or 0.970% 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
230,100 shares and sole power to vote or to direct the voting of 12,300
shares, and no power to vote or to direct the voting of 217,800 shares
of common stock owned by the institutional account(s) as reported
above.

	Strategic Advisers, Inc., 82 Devonshire Street, Boston, MA 02109,
a wholly-owned subsidiary of FMR Corp. and an investment adviser
registered under Section 203 of the Investment Advisers Act of 1940,
provides investment advisory services to individuals. It does not have
sole power to vote or direct the voting of shares of certain securities
held for clients and has sole dispositive power over such securities.
As such, FMR Corp.'s beneficial ownership may include shares
beneficially owned through Strategic Advisers, Inc.

	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 February 14, 2000, 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 Geon Company at
December 31, 1999.

FMR Corp.

By   /s/Eric D. Roiter
	Eric D. Roiter
	Duly authorized under Power of Attorney
	dated December 30, 1997, by and on behalf
	of FMR Corp. and its direct and indirect
	subsidiaries

Edward C. Johnson 3d

By   /s/Eric D. Roiter
	Eric D. Roiter
	Duly authorized under Power of Attorney
	dated December 30, 1997, by and on behalf
	of Edward C. Johnson 3d

Abigail P. Johnson

By   /s/Eric D. Roiter
	Eric D. Roiter
	Duly authorized under Power of Attorney
	dated December 30, 1997, by and on behalf
	of Abigail P. Johnson

Fidelity Management & Research Company

By   /s/Eric D. Roiter
	Eric D. Roiter
	Senior V.P. and General Counsel

	Fidelity Value Fund

By   /s/Eric D. Roiter
	Eric D. Roiter
	Secretary