Schedule II: Valuation and Qualifying Accounts 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	$ 455	$ 763	$ 1,032
Additions/Charged to Expense	7,572	7,682	9,287
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction	7,444	7,990	9,556
Balance at End of Period	583	455	763
Allowance For Contract With Customer [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	162	195	371
Additions/Charged to Expense	85	23	(141)
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction	88	56	35
Balance at End of Period	159	162	195
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	162	126	6
Additions/Charged to Expense	170	72	120
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction	1	36	0
Balance at End of Period	$ 331	$ 162	$ 126