Income Taxes - The Components of Net Deferred Income Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Net deferred income tax assets:
Accrued expenses and reserves	$ 7,180	$ 10,745
Stock-based compensation	3,695	3,312
Software	(3,001)	(4,364)
Goodwill	(6,635)	(5,828)
Net operating loss carryforwards	24,857	29,953
Property and equipment	(8,315)	1,381
Convertible debt securities	19	(3,639)
Deferred revenue	2,606	2,225
State taxes	4,520	3,220
Contingent payments	(2,333)	(1,860)
Foreign exchange gain/loss	2,048	1,776
R&D credit	1,413	1,560
Other	383	(1,720)
Total deferred income tax assets	22,696	30,829
Less: valuation allowance	(19,814)	(21,356)
Net deferred income tax assets	2,882	9,473
Client contracts
Net deferred income tax assets:
Client contracts and related intangibles	$ (3,741)	$ (5,932)