DISCONTINUED OPERATIONS (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended				3 Months Ended	9 Months Ended			1 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	May 31, 2011	Dec. 31, 2010	Sep. 30, 2011 Additional Paid-in Capital [Member]	Sep. 30, 2011 Additional Paid-in Capital [Member]	Sep. 30, 2011 Lone Pine Resources Inc [MEMBER]	Jun. 30, 2011 Lone Pine Resources Inc [MEMBER]	Jun. 30, 2011 Lone Pine Resources Inc [MEMBER] IPO [Member]	Dec. 31, 2010 Lone Pine Resources Inc [MEMBER] IPO [Member]	Jun. 01, 2011 Lone Pine Resources Inc [MEMBER] IPO [Member]	Dec. 31, 2010 Lone Pine Resources Inc [MEMBER]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of common stock sold (as a percent)												19.90%
Dividend Tax Payable, Foreign					$ 28,900,000
Outstanding indebtedness owed to Forest										400,500,000
Common stock sold, price per share, net of underwriting discounts and commissions (in dollars per share)													$ 12.22
Percentage of ownership interest upon completion of offering (as a percent)											82.00%
Number of shares of common stock sold (in shares)											15
Common stock sold, price per share (in dollars per share)													$ 13.00
Net proceeds from the offering after deducting underwriting discounts and commissions and offering expenses											178,200,000
Partial consideration for Forest's contribution of Forest's direct and indirect interest in its Canadian operations											29,200,000
Common stock conversion ratio									0.61248511
Transfers from (to) the noncontrolling interest:
Net earnings attributable to Forest Oil Corporation	82,795,000	68,911,000	118,375,000	211,327,000
Increase in Forest Oil Corporation's capital surplus for sale of 15 million Lone Pine Resources Inc. common shares			178,175,000				(269,000)	112,610,000
Decrease in Forest Oil Corporation's capital surplus for spin-off of 70 million Lone Pine Resources Inc. common shares			(469,935,000)				(333,568,000)	(333,568,000)
Change from net earnings attributable to Forest Oil Corporation and transfers from (to) noncontrolling interest	(251,042,000)		(102,583,000)
Major Classes of Assets and Liabilities Included in the Discontinued Operations
Cash														576,000
Accounts receivable														33,405,000
Other current assets														16,161,000
Current assets of discontinued operations	0		0			50,142,000								50,142,000
Goodwill														17,422,000
Net property and equipment														645,405,000
Other assets														2,222,000
Long-term assets of discontinued operations	0		0			665,049,000								665,049,000
Accounts payable and accrued liabilities														42,202,000
Other current liabilities														3,445,000
Current liabilities of discontinued operations	0		0			45,647,000								45,647,000
Deferred income taxes														57,560,000
Asset retirement obligations														13,741,000
Other long-term liabilities														3,172,000
Long-term liabilities of discontinued operations	0		0			74,473,000								74,473,000
Major Components of Earnings From Discontinued Operations
Total revenues	50,298,000	35,193,000	137,834,000	110,864,000
Direct operating expenses	13,902,000	10,108,000	40,350,000	27,885,000
General and administrative	3,255,000	1,694,000	8,846,000	5,525,000
Depreciation, depletion, and amortization	20,799,000	15,875,000	60,780,000	45,516,000
Interest expense	3,000,000	82,000	3,866,000	274,000
Realized and unrealized gains on derivative instruments, net	(28,498,000)	0	(33,628,000)	0
Other, net	235,000	(9,026,000)	(4,053,000)	(4,561,000)
Earnings from discontinued operations before tax	37,605,000	16,460,000	61,673,000	36,225,000
Income tax	9,497,000	3,120,000	17,104,000	8,664,000
Earnings from discontinued operations, net of tax	$ 28,108,000	$ 13,340,000	$ 44,569,000	$ 27,561,000