Derivative Instruments - Summary of Gross Fair Values of Individual Derivative Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 10	$ 36
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	97	75
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	134	90
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	132
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities		89
Net Amount, Derivative Assets	97	75
Derivative Asset, Fair Value, Gross Asset	97	75
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	134	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	97	75
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	133	90
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	132	89
Net Amount, Derivative Assets	97	75
Derivative Asset, Fair Value, Gross Asset	97	75
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	133	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	0
Derivative liabilities	1	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	1	0
Variable Interest Entity, Primary Beneficiary [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	61	52
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,709	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	61	52
Derivative Asset, Fair Value, Gross Asset	61	52
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	1,709	1,657
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	1,709	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	1,709	1,657
Derivative liabilities	1,709	1,657
Derivative Liabilities Net Amount	1,709	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	61	52
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Net Amount, Derivative Assets	61	52
Derivative Asset, Fair Value, Gross Asset	61	$ 52
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 0