Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Increase (decrease) in valuation of allowance	$ (717,000)	$ (47,917,000)	$ (12,418,000)
Effective tax rate	57.40%	(221.60%)	(140.50%)
Unrealized excess tax benefits from stock options exercised	21,545,000	14,893,000
Unrecognized tax benefit	393,000	393,000
Significant change in uncertain tax benefit reasonably possible amount of unrecorded benefit	0
Accrued interest or penalties	0
U.S. Federal
Income Taxes [Line Items]
Net operating loss carryforwards	165,143,000
Net operating loss carryforwards expiration date description	expire in the years 2025 through 2033
U.S. Federal | Minimum
Income Taxes [Line Items]
Net operating loss carryforwards, expiration year	2025
U.S. Federal | Maximum
Income Taxes [Line Items]
Net operating loss carryforwards, expiration year	2033
State
Income Taxes [Line Items]
Net operating loss carryforwards	86,860,000
Net operating loss carryforwards expiration date description	expire between 2015 and 2033
State | Minimum
Income Taxes [Line Items]
Net operating loss carryforwards, expiration year	2015
Federal alternative tax credit carryover	$ 997,000
State | Maximum
Income Taxes [Line Items]
Net operating loss carryforwards, expiration year	2033