Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 37	$ 41	$ 47
Charged to Costs & Expenses	14	10	9
Charged to Other Accounts	0	0	0
Deductions	20	14	15
Balance at End of Period	31	37	41
Deferred Tax Asset Valuation Allowance [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	415	445	346
Charged to Costs & Expenses	100	0	0
Charged to Other Accounts	0	0	99
Deductions	30	30	0
Balance at End of Period	$ 485	$ 415	$ 445