Derivative Instruments - Summary of Asset and Liability Management Derivative Positions of Company (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Derivative [Line Items]
Notional Value	$ 1,200,000
Asset and Liability Management Positions [Member]
Derivative [Line Items]
Notional Value	86,899	$ 90,763
Fair Value, Assets	389	396
Fair Value, Liabilities	253	422
Asset and Liability Management Positions [Member] | Other Derivatives [Member]
Derivative [Line Items]
Notional Value	2,767	1,908
Fair Value, Assets	11	11
Fair Value, Liabilities	121	190
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value	5,055	9,215
Fair Value, Assets	0
Fair Value, Liabilities	1	3
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value	4,595	9,616
Fair Value, Assets	0
Fair Value, Liabilities	0
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Futures and Forwards [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value	2,945	3,546
Fair Value, Assets	4	10
Fair Value, Liabilities	15	18
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Futures and Forwards [Member] | Written [Member]
Derivative [Line Items]
Notional Value	4,851	7,522
Fair Value, Assets	26	20
Fair Value, Liabilities	7	38
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Options [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value	7,385	11,434
Fair Value, Assets	329	346
Fair Value, Liabilities	0
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value	3,707	7,849
Fair Value, Assets	12	7
Fair Value, Liabilities	100	148
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Notional Value	622	962
Fair Value, Assets	2	2
Fair Value, Liabilities	1	6
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Equity Contracts [Member]
Derivative [Line Items]
Notional Value	209	361
Fair Value, Assets	0
Fair Value, Liabilities	7	10
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Credit Contracts [Member]
Derivative [Line Items]
Notional Value	1,425	330
Fair Value, Assets	0
Fair Value, Liabilities	0
Asset and Liability Management Positions [Member] | Fair Value Hedges [Member] | Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value	9,550	17,400
Fair Value, Assets	0
Fair Value, Liabilities	0	9
Asset and Liability Management Positions [Member] | Fair Value Hedges [Member] | Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value	19,264	5,542
Fair Value, Assets	0
Fair Value, Liabilities	0
Asset and Liability Management Positions [Member] | Cash Flow Hedges [Member] | Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value	23,700	14,300
Fair Value, Assets	0
Fair Value, Liabilities	0
Asset and Liability Management Positions [Member] | Net Investment Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Notional Value	824	$ 778
Fair Value, Assets	5
Fair Value, Liabilities	$ 1