Income Taxes - Summary of Components of Deferred Tax Balances (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Tax credit carry forward	$ 1,474	$ 4,806
Depreciation and amortization	2,183	3,765
Stock-based compensation	7,647	10,385
Accrued employee costs and other expenses	3,673	5,130
Net operating loss carry forwards	2,068	1,856
Unrealized exchange loss	252	2,099
Deferred rent	2,064	1,307
Others	1,007	484
Deferred tax assets	20,368	29,832
Valuation allowance	(108)	(454)
Deferred tax assets	20,260	29,378
Deferred tax liabilities:
Unrealized exchange gain	5,069	1,414
Intangible assets	4,648	13,165
Others	1,958	0
Deferred tax liabilities:	11,675	14,579
Net deferred tax assets	$ 8,585	$ 14,799