Income Taxes - Roll Forward of Liability for Unrecognized Tax Benefits Exclusive of Accrued Interest (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, beginning of period	$ 3,110	$ 2,903		$ 1,982
Increase in previous year tax positions	0	57	659
Increase in current year tax positions	121	144	151
Increase (decrease) related to adjustment of previous estimates of activity	94	6	111
Balance, end of period	$ 3,325	$ 3,110	$ 2,903	$ 1,982