Indebtedness - Summary of Other Non-Recourse Debt (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Non-recourse debt	$ 6,388,000,000	$ 6,795,000,000
Unamortized debt issuance costs, net of premium, and issuance discount	59,000,000	68,000,000
Participating Interest Financing
Debt Instrument [Line Items]
Non-recourse debt	5,319,000,000	5,607,000,000
Trust 2017-2
Debt Instrument [Line Items]
Non-recourse debt	207,000,000	231,000,000
Trust 2018-1
Debt Instrument [Line Items]
Non-recourse debt	252,000,000	284,000,000
Trust 2018-2
Debt Instrument [Line Items]
Non-recourse debt	213,000,000	250,000,000
Trust 2018-3
Debt Instrument [Line Items]
Non-recourse debt	312,000,000	326,000,000
Legacy Asset
Debt Instrument [Line Items]
Non-recourse debt	26,000,000	29,000,000
Other
Debt Instrument [Line Items]
Non-recourse debt	6,329,000,000	$ 6,727,000,000
Nonrecourse debt–legacy assets \| Participating Interest Financing
Debt Instrument [Line Items]
Securitized Amount	0
Nonrecourse debt–legacy assets \| Trust 2017-2
Debt Instrument [Line Items]
Securitized Amount	263,000,000
Nonrecourse debt–legacy assets \| Trust 2018-1
Debt Instrument [Line Items]
Securitized Amount	279,000,000
Nonrecourse debt–legacy assets \| Trust 2018-2
Debt Instrument [Line Items]
Securitized Amount	226,000,000
Nonrecourse debt–legacy assets \| Trust 2018-3
Debt Instrument [Line Items]
Securitized Amount	321,000,000
Nonrecourse debt–legacy assets \| Legacy Asset
Debt Instrument [Line Items]
Securitized Amount	$ 101,000,000

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of unamortized debt discount (premium) and debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(2)
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Amount of debt for which creditor does not have general recourse to the debtor but rather has recourse only to the property used for collateral in the transaction or other specific property.

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