Corporate Restructuring Costs (Schedule of Restructuring Costs) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 9,748	$ 0	$ 28,844	$ 0
Stock-based compensation	[1]	6,087	0	(339)	0
Total restructuring costs		14,759	0	28,532	0
Employee Severance and Other Transition Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		4,100	0	4,593	0
Recruitment and Relocation Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	[1]	3,188	0	3,395	0
Lease Termination Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	[2]	0	0	15,196	0
Third-party and Other Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	[1]	2,460	0	5,660	0
Non-cash Adjustment[Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	[2]	$ (1,076)	$ 0	$ 27	$ 0

[1] Recorded in general and administrative expenses on the condensed consolidated statement of income.

[2] Recorded in impairment, closure costs, and asset disposals on the condensed consolidated statement of income.