Restructuring Charges - Roll-Forward of Accrued Restructuring Expense (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2017	$ 1,210
Payments	(883)
Non-cash settlement	(228)
Accrued at September 30, 2017	99
Severance expenses [Member]
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2017	901
Payments	(832)
Non-cash settlement	0
Accrued at September 30, 2017	69
Write-downs and retirements of fixed assets [Member]
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2017	228
Payments	0
Non-cash settlement	(228)
Accrued at September 30, 2017	0
Lease cancellations [Member]
Restructuring Reserve [Roll Forward]
Accrued at January 1, 2017	81
Payments	(51)
Non-cash settlement	0
Accrued at September 30, 2017	$ 30