Restructuring Charges - Roll-Forward of Accrued Restructuring Expense (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($)
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2017	$ 1,210
Payments	(757)
Accrued at June 30, 2017	453
Severance expenses [Member]
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2017	901
Payments	(713)
Accrued at June 30, 2017	188
Write-downs and retirements of fixed assets [Member]
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2017	228
Payments	0
Accrued at June 30, 2017	228
Lease cancellations [Member]
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2017	81
Payments	(44)
Accrued at June 30, 2017	$ 37