Debt Short-term Financing (Details)	12 Months Ended
	Dec. 31, 2015 USD ($)	Feb. 26, 2015 USD ($)	Dec. 31, 2014 USD ($)
Short-term Financing [Line Items]
Short-term Borrowings	$ 50,000,000		$ 0
Short-term Borrowings, Weighted Average Interest Rate	1.14%
Line of Credit Facility, Remaining Borrowing Capacity	$ 122,000,000
U.S. Commercial Paper Program [Member]
Short-term Financing [Line Items]
Maximum Period to Maturity Allowed Under Program	397 days
Short-term Debt, Period to Maturity	47 days
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 2,000,000,000
Line of Credit Facility, Expiration Date	Jul. 31, 2018
Debt, Covenant, Maximum Consolidated Total Leverage Ratio of Debt to EBITDA	3.5
Debt, Covenant, Minimum Consolidated Interest Coverage Ratio	3.0
Letters of Credit Outstanding, Amount	$ 65,000,000
Line of Credit Facility, Amount Outstanding	$ 0