Schedule of Valuation and Qualifying Accounts Disclosure (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 Year		$ 9	$ 6	$ 2
Charged to Expense		5	4	4
Charged to Other Accounts		1	2	0
Deductions	[1]	(6)	3	0
Balance at End of Year		9	9	6
Deferred Tax Asset Valuation Allowance [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year		1,168	1,581	1,637
Charged to Expense		(168)	(413)	(56)
Charged to Other Accounts		0	0	0
Deductions	[1]	0	0	0
Balance at End of Year		$ 1,000	$ 1,168	$ 1,581

[1] Represents write-offs of accounts considered to be uncollectible and previously reserved.