Income Tax Expense (Income Tax Benefit Computation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax benefit at federal statutory rate	$ (22,732)	$ (52,418)	$ (20,315)
State income tax benefit, net of federal benefit	(1,114)	(2,323)	(937)
Meals and entertainment	454	445	328
Research and development credits	(913)	(2,041)	(1,756)
Stock-based compensation	3,203	2,604	1,633
Derivative loss	0	14,903	0
Contingent consideration	(986)	(850)	34
Foreign tax rate differential	692	1,394	1,013
Net change in valuation allowance	(24,976)	35,678	10,052
Return to provision true-up	5,719	1,981	583
Unrecognized tax benefits	457	971	928
Federal tax rate change	39,807	0	0
Other, net	(70)	154	(900)
Income tax expense (benefit)	$ (459)	$ 498	$ (9,337)