Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Benefit from income taxes	$ 186,897,000	$ 983,000	$ 186,827,000	$ 1,123,000
Deferred tax asset valuation allowance reversed	187,600,000
Deferred tax asset valuation allowance per diluted share reversed	$ 3.80
Deferred tax asset valuation allowance	39,697,000		39,697,000		238,800,000	248,306,000
Pre-tax income	121,700,000		121,700,000
Quarter Three [Member]
Income Taxes [Line Items]
Deferred tax asset valuation allowance reversed			39,700,000
Quarter Four [Member]
Income Taxes [Line Items]
Deferred tax asset valuation allowance reversed			$ 39,700,000
Minimum [Member]
Income Taxes [Line Items]
Recognized tax effect on financial statements, percent			50.00%