Derivative Instruments - Summary of Gross Fair Values of Individual Derivative Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 1	$ 36
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	95	75
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	126	90
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	124
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities		89
Net Amount, Derivative Assets	95	75
Derivative Asset, Fair Value, Gross Asset	95	75
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	126	90
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	2	1
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	94	75
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	125	90
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	124	89
Net Amount, Derivative Assets	94	75
Derivative Asset, Fair Value, Gross Asset	95	75
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	125	89
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	1	1
Other Credit Derivatives [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1
Derivative liabilities	1
Derivative Liability, Fair Value, Amount Offset Against Collateral	0
Derivative Liabilities Net Amount	1
Variable Interest Entity, Primary Beneficiary [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	53	52
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,771	1,657
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities		0
Net Amount, Derivative Assets	53	52
Derivative Asset, Fair Value, Gross Asset	53	52
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	1,771	1,657
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	1,771	1,657
Variable Interest Entity, Primary Beneficiary [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,771	1,657
Derivative liabilities	1,771	1,657
Derivative Liabilities Net Amount	1,771	1,657
Variable Interest Entity, Primary Beneficiary [Member] | Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	53	52
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Net Amount, Derivative Assets	53	52
Derivative Asset, Fair Value, Gross Asset	53	$ 52
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 0