INCOME TAXES (Income Before Income Tax, Domestic and Foreign) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
United States Federal																	$ (1,013,801)	$ 188,421	$ 301,349
Foreign																	(101,693)	(1,026)	(1,917)
Earnings (loss) from continuing operations before income taxes	$ (288,365)	[1]	$ (451,272)	[1]	$ (344,099)	[1]	$ (31,758)	[1]	$ 31,662	[1]	$ 94,166	[1]	$ 75,861	[1]	$ (14,294)	[1]	$ (1,115,494)	$ 187,395	$ 299,432

[1] 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.