Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate	31.60%	38.20%	33.20%	37.00%
Federal statutory income tax rate	35.00%	35.00%	35.00%	35.00%
Unrecognized tax benefits	$ 25,200,000	$ 25,700,000	$ 25,200,000	$ 25,700,000	$ 25,200,000
Unrecognized tax benefits that would impact effective tax rate	0	0	0	0	0
Estimated interest and penalties related to the underpayment of income taxes	0	0	0	0
Accrued interest and penalties related to the underpayment of income taxes	100,000	100,000	100,000	100,000	100,000
Liability for uncertain tax positions, including accrued interest and penalties	$ 25,300,000	$ 25,800,000	$ 25,300,000	$ 25,800,000	$ 25,300,000