Income Taxes - Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Compensation and benefits	$ 23,080	$ 32,021
Depreciation and amortization	1,521	2,483
Cumulative translation adjustment	8,878	20,361
Operating loss carryforwards	10,133	4,944
Capital loss carryforwards	2,106	1,938
Unrealized loss on investments	61	0
Other financial accruals	2,047	2,299
Valuation allowances	(5,481)	(1,938)
Total deferred tax assets	42,345	62,108
Deferred tax liabilities:
Unrealized gain on investments	0	659
Other financial accruals	2,928	3,008
Total deferred tax liabilities	2,928	3,667
Net deferred tax asset	$ 39,417	$ 58,441