Debt (2016 Senior Revolving Credit Agreement) (Details) - Line of Credit - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Nov. 22, 2016
2016 Senior Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit base interest rate	0.20%
Line of Credit Facility, Maximum Borrowing Capacity		$ 2,000.0
Guarantor Obligations, Triggering Amount		500.0
Line of Credit Facility, Interest Rate During Period	1.20%
Line of Credit Facility, Commitment Fee Percentage	0.175%
Line of Credit Facility, Fair Value of Amount Outstanding	$ 0.0
2014 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding	$ 0.0
Subfacility for Swing Line Borrowings | 2016 Senior Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		175.0
Subfacility for Letters of Credit | 2016 Senior Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 200.0
Trailing Four Quarters | 2016 Senior Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Covenant Terms	3.75 to 1.00
Three Full Fiscal Quarters Following Qualifying Acquisition | 2016 Senior Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Covenant Terms	4.25 to 1.00