Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes	$ 6,584,000	$ (644,000)	$ 17,089,000	$ (47,742,000)
Effective income tax rate	39.10%	(5.10%)	36.40%	(166.60%)
Net tax benefit due to change in effective tax rate		47,700,000		47,700,000
Reversal of valuation allowance on deferred tax assets		57,900,000		57,900,000
Income tax expense includes revision of deferred tax estimate from stock options and state tax	$ 85,000		$ (682,000)