Segment Information - Reconciliation of Net Income (Loss) Attributable to AGL to Segment Adjusted Operating Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total revenues	$ 848	$ 1,115	$ 963
Total expenses	465	729	503
Equity in earnings of investees	94	27	4
Provision (Benefit) for Income Taxes	58	45	63
Less: Noncontrolling interests	30	6	(1)
Reconciling items:
Realized gains (losses) on investments	15	18	22
Fair value gains (losses) on committed capital securities	(28)	(1)	(22)
Total consolidated	389	362	402
Revenues
Reconciling items:
Total consolidated	848	1,115	963
Expenses
Reconciling items:
Total consolidated	465	729	503
Equity in Earnings of Investees
Reconciling items:
Total consolidated	94	27	4
Provision (Benefit) for Income Taxes
Reconciling items:
Total consolidated	58	45	63
Nonredeemable Noncontrolling Interests
Reconciling items:
Total consolidated	30	6	(1)
Net Income (Loss) Attributable to AGL
Reconciling items:
Total consolidated	389	362	402
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	816	940	939
Total expenses	141	574	358
Equity in earnings of investees	144	61	2
Provision (Benefit) for Income Taxes	116	48	81
Less: Noncontrolling interests	0	0	0
Segment adjusted operating income (loss)	703	379	502
Operating Segments | Insurance
Segment Reporting Information [Line Items]
Total revenues	733	874	917
Total expenses	33	446	324
Equity in earnings of investees	144	61	2
Provision (Benefit) for Income Taxes	122	60	83
Less: Noncontrolling interests	0	0	0
Segment adjusted operating income (loss)	722	429	512
Operating Segments | Asset Management
Segment Reporting Information [Line Items]
Total revenues	83	66	22
Total expenses	108	128	34
Equity in earnings of investees	0	0	0
Provision (Benefit) for Income Taxes	(6)	(12)	(2)
Less: Noncontrolling interests	0	0	0
Segment adjusted operating income (loss)	(19)	(50)	(10)
Corporate division
Segment Reporting Information [Line Items]
Total revenues	2	9	3
Total expenses	312	132	133
Equity in earnings of investees	0	(6)	0
Provision (Benefit) for Income Taxes	(47)	(18)	(19)
Less: Noncontrolling interests	0	0	0
Segment adjusted operating income (loss)	(263)	(111)	(111)
Other
Segment Reporting Information [Line Items]
Total revenues	142	40	22
Total expenses	26	21	25
Equity in earnings of investees	(50)	(28)	2
Provision (Benefit) for Income Taxes	6	(3)	0
Less: Noncontrolling interests	30	6	(1)
Segment adjusted operating income (loss)	30	(12)	0
Realized gains (losses) on investments | Revenues
Reconciling items:
Realized gains (losses) on investments	15	18	22
Realized gains (losses) on investments | Expenses
Reconciling items:
Realized gains (losses) on investments	0	0	0
Realized gains (losses) on investments | Equity in Earnings of Investees
Reconciling items:
Realized gains (losses) on investments	0	0	0
Realized gains (losses) on investments | Provision (Benefit) for Income Taxes
Reconciling items:
Realized gains (losses) on investments	0	0	0
Realized gains (losses) on investments | Nonredeemable Noncontrolling Interests
Reconciling items:
Realized gains (losses) on investments	0	0	0
Realized gains (losses) on investments | Net Income (Loss) Attributable to AGL
Reconciling items:
Realized gains (losses) on investments	15	18	22
Non-credit impairment-related unrealized fair value gains (losses) on credit derivatives | Revenues
Reconciling items:
Non-credit Impairment-Related Unrealized Fair Value Gains (Losses) on Credit Derivatives	(78)	67	(23)
Non-credit impairment-related unrealized fair value gains (losses) on credit derivatives | Expenses
Reconciling items:
Non-credit Impairment-Related Unrealized Fair Value Gains (Losses) on Credit Derivatives	(14)	2	(13)
Non-credit impairment-related unrealized fair value gains (losses) on credit derivatives | Equity in Earnings of Investees
Reconciling items:
Non-credit Impairment-Related Unrealized Fair Value Gains (Losses) on Credit Derivatives	0	0	0
Non-credit impairment-related unrealized fair value gains (losses) on credit derivatives | Provision (Benefit) for Income Taxes
Reconciling items:
Non-credit Impairment-Related Unrealized Fair Value Gains (Losses) on Credit Derivatives	0	0	0
Non-credit impairment-related unrealized fair value gains (losses) on credit derivatives | Nonredeemable Noncontrolling Interests
Reconciling items:
Non-credit Impairment-Related Unrealized Fair Value Gains (Losses) on Credit Derivatives	0	0	0
Non-credit impairment-related unrealized fair value gains (losses) on credit derivatives | Net Income (Loss) Attributable to AGL
Reconciling items:
Non-credit Impairment-Related Unrealized Fair Value Gains (Losses) on Credit Derivatives	(64)	65	(10)
Fair value gains (losses) on CCS | Revenues
Reconciling items:
Fair value gains (losses) on committed capital securities	(28)	(1)	(22)
Fair value gains (losses) on CCS | Expenses
Reconciling items:
Fair value gains (losses) on committed capital securities	0	0	0
Fair value gains (losses) on CCS | Equity in Earnings of Investees
Reconciling items:
Fair value gains (losses) on committed capital securities	0	0	0
Fair value gains (losses) on CCS | Provision (Benefit) for Income Taxes
Reconciling items:
Fair value gains (losses) on committed capital securities	0	0	0
Fair value gains (losses) on CCS | Nonredeemable Noncontrolling Interests
Reconciling items:
Fair value gains (losses) on committed capital securities	0	0	0
Fair value gains (losses) on CCS | Net Income (Loss) Attributable to AGL
Reconciling items:
Fair value gains (losses) on committed capital securities	(28)	(1)	(22)
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves | Revenues
Reconciling items:
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves	(21)	42	22
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves | Expenses
Reconciling items:
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves	0	0	0
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves | Equity in Earnings of Investees
Reconciling items:
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves	0	0	0
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves | Provision (Benefit) for Income Taxes
Reconciling items:
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves	0	0	0
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves | Nonredeemable Noncontrolling Interests
Reconciling items:
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves	0	0	0
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves | Net Income (Loss) Attributable to AGL
Reconciling items:
Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves	(21)	42	22
Tax effect | Revenues
Reconciling items:
Tax effect	0	0	0
Tax effect | Expenses
Reconciling items:
Tax effect	0	0	0
Tax effect | Equity in Earnings of Investees
Reconciling items:
Tax effect	0	0	0
Tax effect | Provision (Benefit) for Income Taxes
Reconciling items:
Tax effect	17	(18)	(1)
Tax effect | Nonredeemable Noncontrolling Interests
Reconciling items:
Tax effect	0	0	0
Tax effect | Net Income (Loss) Attributable to AGL
Reconciling items:
Tax effect	(17)	18	1
Subtotal
Segment Reporting Information [Line Items]
Total revenues	960	989	964
Total expenses	479	727	516
Equity in earnings of investees	94	27	4
Provision (Benefit) for Income Taxes	75	27	62
Less: Noncontrolling interests	30	6	(1)
Segment adjusted operating income (loss)	$ 470	$ 256	$ 391