New Accounting Standards (Details) - USD ($) $ in Millions	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for expected credit losses	$ 99		$ 33
Retained earnings (accumulated deficit)	$ 51		$ (25)
Cumulative Effect, Period Of Adoption, Adjustment, Pre-tax
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for expected credit losses		$ 62
Retained earnings (accumulated deficit)		(65)
Cumulative Effect, Period Of Adoption, Adjustment, Tax
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings (accumulated deficit)		14
Financing Receivables and Unfunded Loan Commitments | Cumulative Effect, Period Of Adoption, Adjustment, Pre-tax
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for expected credit losses		$ 65