SHAREHOLDERS' EQUITY (Lone Pine Initial Public Offering and Spin-off) (Details) (USD $)	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Sep. 30, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jun. 01, 2011
Initial Public Offering and Spin-off - Lone Pine Resources Inc.
Percentage of subsidiary common stock sold in initial public offering (as a percent)													18.00%
Dividend tax payable to Canadian federal tax authorities					$ 28,900,000
Partial consideration for Forest's contribution of Forest's direct and indirect interest in its Canadian operations					29,200,000
Outstanding indebtedness owed to Forest					400,500,000
Percentage of subsidiary stock distributed to shareholders in spin-off (as a percent)			82.00%						82.00%
Common stock conversion ratio			0.61248511						0.61248511
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Net
Net earnings attributable to Forest Oil Corporation common shareholders	19,467,000	[1],[2]	82,795,000	[1],[2]	38,910,000	[1],[2]	(3,330,000)	[1],[2]	118,375,000	(1,288,931,000)	137,842,000	227,521,000
Transfers from (to) the noncontrolling interest:
Increase in Forest Oil Corporation’s capital surplus for sale of 15 million Lone Pine Resources Inc. common shares					178,175,000				112,610,000		178,175,000
Decrease in Forest Oil Corporation’s capital surplus for spin-off of 70 million Lone Pine Resources Inc. common shares									(333,568,000)		(469,935,000)
Change from net earnings attributable to Forest Oil Corporation common shareholders and transfers from (to) noncontrolling interest									$ (102,583,000)
Number of shares of common stock sold in IPO resulting in a change in capital surplus of parent (in shares)									15,000,000
Common shares spun off resulting in a change in capital surplus of parent (in shares)									70,000,000

[1] Upon completion of Lone Pine’s initial public offering on June 1, 2011, Forest maintained a controlling interest in Lone Pine until it was spun-off on September 30, 2011. As such, during the second and third quarters of 2011, Forest had net earnings attributable to the noncontrolling interest.

[2] Earnings (loss) before income taxes, net earnings (loss), and net earnings (loss) attributable to Forest Oil Corporation common shareholders have been impacted by non-cash ceiling test write-downs in every quarter of 2012 as discussed in Note 1 and are also subject to large fluctuations due to Forest’s election not to use cash flow hedge accounting for derivative instruments as discussed in Note 9.