Segment Information - Reconciliation of Net Income (Loss) Attributable to AGL to Segment Adjusted Operating Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Revenues	$ 283	$ 300
Expenses	165	196
Equity in Earnings (Losses) of Investees	2	(11)
Less: Provision (benefit) for income taxes	23	18
Less: Noncontrolling interests	16	9
Net Income (Loss) Attributable to AGL	81	66
Subtotal
Segment Reporting Information [Line Items]
Revenues	268	332
Expenses	165	200
Equity in Earnings (Losses) of Investees	2	(11)
Less: Provision (benefit) for income taxes	21	22
Less: Noncontrolling interests	16	9
Net Income (Loss) Attributable to AGL	68	90
Operating Segments
Segment Reporting Information [Line Items]
Revenues	231	317
Expenses	121	161
Equity in Earnings (Losses) of Investees	30	(1)
Less: Provision (benefit) for income taxes	24	22
Less: Noncontrolling interests	0	0
Net Income (Loss) Attributable to AGL	116	133
Operating Segments | Insurance
Segment Reporting Information [Line Items]
Revenues	190	278
Expenses	79	122
Equity in Earnings (Losses) of Investees	30	(1)
Less: Provision (benefit) for income taxes	24	22
Less: Noncontrolling interests	0	0
Net Income (Loss) Attributable to AGL	117	133
Operating Segments | Asset Management
Segment Reporting Information [Line Items]
Revenues	41	39
Expenses	42	39
Equity in Earnings (Losses) of Investees	0	0
Less: Provision (benefit) for income taxes	0	0
Less: Noncontrolling interests	0	0
Net Income (Loss) Attributable to AGL	(1)	0
Corporate division
Segment Reporting Information [Line Items]
Revenues	2	1
Expenses	48	34
Equity in Earnings (Losses) of Investees	0	0
Less: Provision (benefit) for income taxes	(2)	0
Less: Noncontrolling interests	0	0
Net Income (Loss) Attributable to AGL	(44)	(33)
Other
Segment Reporting Information [Line Items]
Revenues	35	14
Expenses	(4)	5
Equity in Earnings (Losses) of Investees	(28)	(10)
Less: Provision (benefit) for income taxes	(1)	0
Less: Noncontrolling interests	16	9
Net Income (Loss) Attributable to AGL	(4)	(10)
Reconciling items: | Realized gains (losses) on investments
Segment Reporting Information [Line Items]
Revenues	(2)	3
Expenses	0	0
Equity in Earnings (Losses) of Investees	0	0
Less: Provision (benefit) for income taxes	0	0
Less: Noncontrolling interests	0	0
Net Income (Loss) Attributable to AGL	(2)	3
Reconciling items: | Non-credit impairment-related unrealized fair value gains (losses) on credit derivatives
Segment Reporting Information [Line Items]
Revenues	13	(7)
Expenses	0	(4)
Equity in Earnings (Losses) of Investees	0	0
Less: Provision (benefit) for income taxes	0	0
Less: Noncontrolling interests	0	0
Net Income (Loss) Attributable to AGL	13	(3)
Reconciling items: | Fair value gains (losses) on CCS
Segment Reporting Information [Line Items]
Revenues	(16)	1
Expenses	0	0
Equity in Earnings (Losses) of Investees	0	0
Less: Provision (benefit) for income taxes	0	0
Less: Noncontrolling interests	0	0
Net Income (Loss) Attributable to AGL	(16)	1
Reconciling items: | Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves
Segment Reporting Information [Line Items]
Revenues	20	(29)
Expenses	0	0
Equity in Earnings (Losses) of Investees	0	0
Less: Provision (benefit) for income taxes	0	0
Less: Noncontrolling interests	0	0
Net Income (Loss) Attributable to AGL	20	(29)
Reconciling items: | Tax effect
Segment Reporting Information [Line Items]
Revenues	0	0
Expenses	0	0
Equity in Earnings (Losses) of Investees	0	0
Less: Provision (benefit) for income taxes	(2)	4
Less: Noncontrolling interests	0	0
Net Income (Loss) Attributable to AGL	$ 2	$ (4)