Corporate Restructuring Costs (Reconciliation of Restructuring Liability) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, beginning balance	$ 0
Charges	28,844
Payments	(9,280)
Restructuring Reserve, ending balance	19,564
Employee Severance and Other Transition Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, beginning balance
Charges	4,593
Payments	(339)
Restructuring Reserve, ending balance	4,254
Recruitment and Relocation Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, beginning balance	0
Charges	3,395
Payments	(3,189)
Restructuring Reserve, ending balance	206
Lease Termination Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, beginning balance	0
Charges	15,196
Payments	(499)
Restructuring Reserve, ending balance	14,697
Third-party and Other Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, beginning balance	0
Charges	5,660
Payments	(5,253)
Restructuring Reserve, ending balance	$ 407