Other comprehensive (loss) income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Before-Tax Amount
Foreign currency translation adjustments	$ (2,385)	$ (16,022)	$ (10,405)
Unrealized net gains on investments:
Change in unrealized net gains on investments	544	(5,757)	15,066
Less: reclassification adjustment for net gains included in net income (loss)	(2,940)	(2,501)	(853)
Net unrealized gains (losses)	(2,396)	(8,258)	14,213
Other comprehensive (loss) income	(4,781)	(24,280)	3,808
Tax Expense (Benefit)
Foreign currency translation adjustments	982	(4,877)	(2,840)
Unrealized net gains on investments:
Change in unrealized net gains on investments	190	(2,016)	5,273
Less: reclassification adjustment for net gains included in net income (loss)	(1,029)	(875)	(298)
Net unrealized gains (losses)	(839)	(2,891)	4,975
Other comprehensive (loss) income	143	(7,768)	2,135
Net-of-Tax Amount
Foreign currency translation adjustments	(3,367)	(11,145)	(7,565)
Unrealized net gains on investments:
Change in unrealized net gains on investments	354	(3,741)	9,793
Less: reclassification adjustment for net gains included in net income (loss)	(1,911)	(1,626)	(555)
Net unrealized gains (losses)	(1,557)	(5,367)	9,238
Other comprehensive (loss) income	$ (4,924)	$ (16,512)	$ 1,673