Restructuring - Summary of Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Total Restructuring Expenses	$ 13,281	$ 906
Right-of-Use Asset Impairment and Operating Lease Charges
Restructuring Cost and Reserve [Line Items]
Total Restructuring Expenses	9,522	719
Fixed Asset Impairment
Restructuring Cost and Reserve [Line Items]
Total Restructuring Expenses	1,497	0
Severance
Restructuring Cost and Reserve [Line Items]
Total Restructuring Expenses	1,136	514
Other Expenses
Restructuring Cost and Reserve [Line Items]
Total Restructuring Expenses	1,126	0
Other Expenses
Restructuring Cost and Reserve [Line Items]
Total Restructuring Expenses	$ 0	$ (327)