Schedule II Valuation and Qualifying Accounts (Details) - SEC Schedule, 12-09, Allowance, Notes Receivable [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount	$ 88	$ 64	$ 59	$ 56
SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense	39	20	15
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction	13	14	14
SEC Schedule, 12-09, Valuation Allowances and Reserves, Increase (Decrease) Adjustment	$ 2	$ 1	$ (2)