Supplementary Information Allowance for Uncollectible Accounts Receivable (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Valuation Allowances and Reserves, Balance		$ 113	$ 108	$ 106	$ 84
Expense		48	32	102
Valuation Allowances and Reserves, Recoveries		1	4	12
Valuation Allowances and Reserves, Deductions	[1]	$ 42	$ 26	$ 68

[1] Includes write-offs and amounts reclassified to assets held for sale.