Liabilities - Restructuring Accruals (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Jun. 30, 2018 employee	Sep. 30, 2019 USD ($)
Restructuring Accruals
Number of employees terminated | employee	40
Changes in restructuring accrual
Balance at the beginning of the period		$ 2,213
Provision		3,874
Payments		(4,470)
Balance at the end of the period		1,617
Personnel severance and related costs
Changes in restructuring accrual
Balance at the beginning of the period		2,143
Provision		3,681
Payments		(4,207)
Balance at the end of the period		1,617
Facility Related Costs and Other
Changes in restructuring accrual
Balance at the beginning of the period		70
Provision		193
Payments		$ (263)