Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts, Current [Member]
Valuation Allowance [Line Items]
Beginning Balance	$ 10	$ 11	$ 6
Additions	4	4	5
Net Deductions and Other	6	5
Ending Balance	8	10	11
Valuation Allowance of Deferred Tax Assets [Member]
Valuation Allowance [Line Items]
Beginning Balance	1,201	1,127	953
Additions	176	182	257
Net Deductions and Other	168	108	83
Ending Balance	$ 1,209	$ 1,201	$ 1,127