Income Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010	Dec. 31, 2011
Income Taxes [Line Items]
Statutory Federal income tax rate	34.00%	34.00%	34.00%
Deductions taken for tax purposes on stock option exercises	$ 1,831	$ 2,074
Stock option exercises included in net operating loss carryforwards	7,075	3,599
Tax benefit due to a change in tax law		1,300
Total unrecognized tax benefits	4,651	2,241	2,191		1,678
Preferred Financing
Income Taxes [Line Items]
Net operating loss carryforward annual limitation	591
Net operating loss carryforward expected to expire	6,025
Net operating loss expired	13,324
Net operating loss additional amount utilizable				4,044
U.S. Federal
Income Taxes [Line Items]
Stock option exercises included in net operating loss carryforwards	$ 21,856