Accumulated Other Comprehensive Income - Changes in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	$ 509,457	$ 563,352	$ 492,868
Other comprehensive (loss) income	810	(792)	(92)
Balance	321,673	509,457	563,352
Unrealized Gains and (Losses) on Securities Available-for-Sale [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	(465)	(107)
Unrealized net gain (loss) on available-for-sale securities and foreign currency translation adjustments, net of tax	241	(358)
Amounts reclassified from accumulated other comprehensive loss	0	0
Other comprehensive (loss) income	241	(358)
Balance	(224)	(465)	(107)
Other comprehensive income (loss), before reclassifications, tax	(32)	71
Foreign Currency Translation Adjustments [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	(569)	(135)
Unrealized net gain (loss) on available-for-sale securities and foreign currency translation adjustments, net of tax	569	(434)
Amounts reclassified from accumulated other comprehensive loss	0	0
Other comprehensive (loss) income	569	(434)
Balance	0	(569)	$ (135)
Other comprehensive income (loss), before reclassifications, tax	$ (348)	$ 266