Insurance - Unearned Insurance Premium Reserves, Claim Reserves and Benefit Reserves (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Claim reserves	$ 148	$ 117	$ 117	$ 154
Subtotal	621	649
Total	1,392	1,442
Non-finance receivable related
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Subtotal	385	403
Payable to OMH | Finance receivable related
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unearned premium reserves	662	712
Claim reserves	109	81
Subtotal	771	793
Payable to third-party beneficiaries | Finance receivable related
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Subtotal	$ 236	$ 246