Debt and Banking Arrangements Credit Facilities and Commercial Paper (Details 2) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015
Credit Facility and Commercial Paper [Line Items]
Commercial paper, outstanding		$ 2	$ 499
Credit facility, capacity	[1]	3,500
Credit facility, loans outstanding	[1]	1,230
Commercial Paper [Member]
Credit Facility and Commercial Paper [Line Items]
Commercial paper, outstanding		2
Credit facility, capacity		$ 3,000
Commercial paper, weighted average interest rate		1.30%
Letters Of Credit Under Certain Bilateral Bank Agreements [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, letters of credit outstanding		$ 1

[1] In managing our available liquidity, we do not expect a maximum outstanding amount in excess of the capacity of our credit facility inclusive of any outstanding amounts under our commercial paper program.