Debt (2016 Term Credit Agreement) (Narrative) (Details) - 2016 Term Loans - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2016		Jun. 30, 2017		Nov. 22, 2016
Debt Instrument [Line Items]
Long-term Debt	$ 1,600.0	[1]	$ 275.0	[1]	$ 2,000.0
Repayments of Debt	$ 400.0		$ 550.0
Debt Instrument, Interest Rate During Period			1.375%
Line of credit base interest rate			0.375%

[1] The 2016 Term Loans mature on November 22, 2019 and bear interest at LIBOR (determined in accordance with the 2016 Term Credit Agreement) plus 1.375% per annum. At June 30, 2017, the weighted average interest rate of the 2016 Term Loans was approximately 2.59%.