Components of Income Tax Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Components Of Income Tax Expense Benefit [Line Items]
Current	$ (40,562)	$ 29,682	$ 20,167
Deferred	88,109	61,835	(8,266)
Income tax expense (benefit)	$ 47,547	$ 91,517	$ 11,901