Employee Benefit Plans (Contributions to Defined Contribution Plans) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contributions to defined contribution plans	$ 18,100,000	$ 16,300,000	$ 16,100,000
Discontinued Operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contributions to defined contribution plans	$ 18,100,000.0