Debt (Revolving Credit Facility And Commercial Paper) (Details) - USD ($) $ in Millions	Jan. 01, 2021	Sep. 30, 2016	Dec. 31, 2015
Outstanding commercial paper obligations		$ 187.0	$ 0.0
Revolving Credit Facility [Member]
Revolving credit facility expiration date	Jan. 01, 2021
Line of Credit Facility, Current Borrowing Capacity		1,250.0
Line of Credit Facility, Maximum Borrowing Capacity		1,750.0
Other Short-term Borrowings		0.0
Letters of Credit Outstanding, Amount		44.0
Outstanding commercial paper obligations		187.0
Line of Credit Facility, Remaining Borrowing Capacity		1,019.0
Letter of Credit [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity		100.0
Competitive Bid Loans [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity		$ 500.0