Income Taxes - Reconciliation to Statutory Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Income tax expense (benefit) at U.S. statutory rates	$ (16,396)	$ (91,105)	$ (31,147)
State taxes, net of U.S. federal impact	(835)	(2,848)	(2,523)
Effect of international operations	785	11,847	10,158
Research and development tax credit	(1,692)	(2,230)	620
Net change in valuation allowance	15,098	7,747	1,883
Change in accrual for unrecognized tax benefits	1,232	2,868	(4,772)
Share-based compensation	1,947	1,848	99
Tax reform impact		(1,690)	(11,344)
Asset impairment	495	46,872
Other	143	(55)	(568)
Total expense (benefit) for income taxes	$ 777	$ (26,746)	$ (37,594)