Segment Information - Reconciliation of Net Income (Loss) Attributable to AGL to Segment Adjusted Operating Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 41	$ 212	$ 431	$ 585
Expenses	43	230	351	506
Equity in Earnings (Losses) of Investees	(20)	23	(31)	66
Less: Provision (benefit) for income taxes	(27)	(15)	(6)	8
Less: Noncontrolling interests	(6)	3	25	11
Net Income (Loss) Attributable to AGL	11	17	30	126
Subtotal
Segment Reporting Information [Line Items]
Revenues	182	228	689	678
Expenses	44	228	356	513
Equity in Earnings (Losses) of Investees	(20)	23	(31)	66
Less: Provision (benefit) for income taxes	(9)	(14)	24	23
Less: Noncontrolling interests	(6)	3	25	11
Net Income (Loss) Attributable to AGL	133	34	253	197
Operating Segments
Segment Reporting Information [Line Items]
Revenues	168	209	652	611
Expenses	8	7	238	213
Equity in Earnings (Losses) of Investees	(11)	33	(46)	100
Less: Provision (benefit) for income taxes	(7)	28	24	69
Less: Noncontrolling interests	0	0	0	0
Net Income (Loss) Attributable to AGL	156	207	344	429
Operating Segments | Insurance
Segment Reporting Information [Line Items]
Revenues	147	190	564	551
Expenses	(16)	(22)	147	131
Equity in Earnings (Losses) of Investees	(11)	33	(46)	100
Less: Provision (benefit) for income taxes	(7)	31	24	75
Less: Noncontrolling interests	0	0	0	0
Net Income (Loss) Attributable to AGL	159	214	347	445
Operating Segments | Asset Management
Segment Reporting Information [Line Items]
Revenues	21	19	88	60
Expenses	24	29	91	82
Equity in Earnings (Losses) of Investees	0	0	0	0
Less: Provision (benefit) for income taxes	0	(3)	0	(6)
Less: Noncontrolling interests	0	0	0	0
Net Income (Loss) Attributable to AGL	(3)	(7)	(3)	(16)
Corporate division
Segment Reporting Information [Line Items]
Revenues	1	1	3	1
Expenses	34	211	104	279
Equity in Earnings (Losses) of Investees	0	1	0	1
Less: Provision (benefit) for income taxes	(3)	(40)	(3)	(45)
Less: Noncontrolling interests	0	0	0	0
Net Income (Loss) Attributable to AGL	(30)	(169)	(98)	(232)
Other
Segment Reporting Information [Line Items]
Revenues	13	18	34	66
Expenses	2	10	14	21
Equity in Earnings (Losses) of Investees	(9)	(11)	15	(35)
Less: Provision (benefit) for income taxes	1	(2)	3	(1)
Less: Noncontrolling interests	(6)	3	25	11
Net Income (Loss) Attributable to AGL	7	(4)	7	0
Reconciling items: | Realized gains (losses) on investments
Segment Reporting Information [Line Items]
Revenues	(14)	3	(39)	4
Expenses	0	0	0	0
Equity in Earnings (Losses) of Investees	0	0	0	0
Less: Provision (benefit) for income taxes	0	0	0	0
Less: Noncontrolling interests	0	0	0	0
Net Income (Loss) Attributable to AGL	(14)	3	(39)	4
Reconciling items: | Non-credit impairment-related unrealized fair value gains (losses) on credit derivatives
Segment Reporting Information [Line Items]
Revenues	(50)	11	(51)	(48)
Expenses	(1)	2	(5)	(7)
Equity in Earnings (Losses) of Investees	0	0	0	0
Less: Provision (benefit) for income taxes	0	0	0	0
Less: Noncontrolling interests	0	0	0	0
Net Income (Loss) Attributable to AGL	(49)	9	(46)	(41)
Reconciling items: | Fair value gains (losses) on CCS
Segment Reporting Information [Line Items]
Revenues	1	(3)	12	(28)
Expenses	0	0		0
Equity in Earnings (Losses) of Investees	0	0	0	0
Less: Provision (benefit) for income taxes	0	0	0	0
Less: Noncontrolling interests	0	0	0	0
Net Income (Loss) Attributable to AGL	1	(3)	12	(28)
Reconciling items: | Foreign exchange gains (losses) on remeasurement of premiums receivable and loss and LAE reserves
Segment Reporting Information [Line Items]
Revenues	(78)	(27)	(180)	(21)
Expenses	0	0	0	0
Equity in Earnings (Losses) of Investees	0	0	0	0
Less: Provision (benefit) for income taxes	0	0	0	0
Less: Noncontrolling interests	0	0	0	0
Net Income (Loss) Attributable to AGL	(78)	(27)	(180)	(21)
Reconciling items: | Tax effect
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Expenses	0	0	0	0
Equity in Earnings (Losses) of Investees	0	0	0	0
Less: Provision (benefit) for income taxes	18	1	30	15
Less: Noncontrolling interests	0	0	0	0
Net Income (Loss) Attributable to AGL	$ (18)	$ (1)	$ (30)	$ (15)