Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			$ 321,673	$ 509,457
Other comprehensive income (loss)	$ 48	$ (50)	184	799
Ending Balance	600,674	469,799	600,674	469,799
Unrealized Net Gains and (Losses) on Securities Available-for- Sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			(224)	(465)
Other comprehensive income (loss), before reclassifications			172	230
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Other comprehensive income (loss)			172	230
Ending Balance	(52)	(235)	(52)	(235)
Other comprehensive income (loss), before reclassifications, tax			(115)	(140)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			0	(569)
Other comprehensive income (loss), before reclassifications			12	569
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Other comprehensive income (loss)			12	569
Ending Balance	$ 12	$ 0	$ 12	0
Other comprehensive income (loss), before reclassifications, tax				$ (348)