Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Loss Carryforwards [Line Items]
Federal income tax rate	34.00%	34.00%	34.00%
Federal net operating loss carryforwards expiration period start	2020
Federal net operating loss carryforwards expiration period end	2033
State operating loss carryforwards expiration period start	2014
State net operating loss carryingforwards period end	2033
State net operating loss carryingforwards expiration year	2015
State net operating loss carryingforwards expiring in initial year	$ 2,200,000
Gross deferred tax assets attributable to stock option exercises and vesting of restricted stock units	3,600,000	5,200,000
Valuation allowance	1,400,000	1,400,000
Reversal of valuation allowance	144,000,000
Unrecognized tax benefits due to uncertain tax positions	6,400,000	6,400,000	6,400,000
Unrecognized tax benefits which would effect effective tax rate if recognized	900,000
Accrued interest and penalties related to uncertain tax positions	0
Stock Options And Restricted Stock Units
Operating Loss Carryforwards [Line Items]
Gross deferred tax assets attributable to stock option exercises and vesting of restricted stock units	1,400,000	3,000,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Federal Net operating loss carrying forward	331,000,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Federal Net operating loss carrying forward	$ 246,000,000