Net Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Deferred tax assets (liabilities):
Net foreign deferred taxes, primarily depreciation	$ (35,274)	$ (30,233)
Depreciation	(82,847)	(80,318)
Intangible drilling costs	(52,748)	(34,156)
Net operating loss carryforward - U.S.	131,111	95,536
Tax monetization transaction	(21,117)	(26,092)
Lease transaction	4,582	5,609
Investment tax credits	1,971	1,971
Production tax credits	59,849	48,255
Stock options amortization	2,934	2,276
Accrued liabilities and other	649	5,468
Deferred Tax Assets (Liabilities), Gross, Total	9,110	(11,684)
Less - valuation allowance	(61,933)	(433)
Total	$ (52,823)	$ (12,117)