Derivative Instruments - Summary of Gross Fair Values of Individual Derivative Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 80	$ 36
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	88	75
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	137	90
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	134
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities		89
Net Amount, Derivative Assets	88	75
Derivative Asset, Fair Value, Gross Asset	89	75
Derivative Asset, Fair Value, Amount Offset Against Collateral	1	0
Derivative liabilities	138	90
Derivative Liability, Fair Value, Amount Offset Against Collateral	1	0
Derivative Liabilities Net Amount	3	1
Variable Interest Entity, Primary Beneficiary [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	62	52
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,610	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	62	52
Derivative Asset, Fair Value, Gross Asset	62	52
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	1,610	1,657
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	1,610	1,657
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	88	75
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	135	90
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	134	89
Net Amount, Derivative Assets	88	75
Derivative Asset, Fair Value, Gross Asset	89	75
Derivative Asset, Fair Value, Amount Offset Against Collateral	1	0
Derivative liabilities	136	89
Derivative Liability, Fair Value, Amount Offset Against Collateral	1	0
Derivative Liabilities Net Amount	1	1
Interest Rate Swap [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,610	1,657
Derivative liabilities	1,610	1,657
Derivative Liabilities Net Amount	1,610	1,657
Other Credit Derivatives [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	2	0
Derivative liabilities	2	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	2	0
Currency Swaps [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	62	52
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Net Amount, Derivative Assets	62	52
Derivative Asset, Fair Value, Gross Asset	62	$ 52
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 0