Income Taxes - Income Tax Benefit Computation (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax benefit at federal statutory rate	$ (14,591)	$ (16,680)	$ (22,732)
State income tax benefit, net of federal benefit	(1,160)	(1,756)	(1,114)
Meals and entertainment	178	230	454
Research and development credits	(931)	(1,211)	(913)
Stock-based compensation	1,825	2,016	3,203
163(l) limited interest expense	4,391	994	0
Contingent consideration	(357)	(1,491)	(986)
Foreign tax rate differential	(269)	(405)	692
Net change in valuation allowance	2,899	16,360	(24,976)
Return to provision	2,387	1,612	5,719
Unrecognized tax benefits	466	605	457
Federal tax rate change	0	0	39,807
NOL expiration and other, net	437	10	(70)
Income tax expense (benefit)	$ (4,725)	$ 284	$ (459)

Effective Income Tax Rate Reconciliation, NOL Expiration and Other, Net, Amount

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