Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 19	$ 18	$ 16
Charged to Costs & Expenses	32	10	2
Charged to Other Accounts	0	0	0
Deductions	4	9	0
Balance at End of Period	47	19	18
Deferred Tax Asset Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	294	364	399
Charged to Costs & Expenses	0	0	0
Charged to Other Accounts	52	0	0
Deductions	0	70	35
Balance at End of Period	$ 346	$ 294	$ 364