Derivative Instruments - Summary of Gross Fair Values of Individual Derivative Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 4	$ 1
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	74	93
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	86	114
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	85
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities		113
Net Amount, Derivative Assets	74	93
Derivative Asset, Fair Value, Gross Asset	74	93
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	86	114
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	1	1
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	73	93
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	85	114
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	85	113
Net Amount, Derivative Assets	73	93
Derivative Asset, Fair Value, Gross Asset	73	93
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	85	114
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	0
Derivative liabilities	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0
Derivative Liabilities Net Amount	0
Variable Interest Entity, Primary Beneficiary [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	38	41
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,739	1,835
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	38	41
Derivative Asset, Fair Value, Gross Asset	38	41
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	1,739	1,835
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	1,739	1,835
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	1,739	1,835
Derivative liabilities	1,739	1,835
Derivative Liabilities Net Amount	1,739	1,835
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	38	41
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Net Amount, Derivative Assets	38	41
Derivative Asset, Fair Value, Gross Asset	38	$ 41
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 0