Income Taxes - Effective Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax expense (benefit) at U.S. federal income tax rate	$ 11,243	$ 5,364	$ (7,270)
State income taxes, net of federal income tax effect	1,028	449	500
Federal and state deferred tax rate change	(5,375)	0	0
Transition tax	5,323	0	0
Effect of non-US operations	(2,143)	(501)	(254)
Nontaxable contingent liability fair value changes and goodwill impairment	237	3,578	13,083
Research and development credit	(38)	(297)	(422)
Change in valuation allowances	2,103	2,206	5,173
Prior year provision to return adjustment	(424)	(137)	372
Write-off of deferred taxes and tax receivables	263	0	858
Change in valuation allowances	914	293	252
Prior year provision to return adjustment	$ 13,131	$ 10,955	$ 12,292