Shareholders' Equity - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 15,201	$ 17,471
Other comprehensive income (loss) before reclassifications, after tax	262	(1,011)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	27	9
Other comprehensive income (loss)	289	(1,002)
Amounts attributable to noncontrolling interests	(31)	106
Balance at end of period	15,314	16,576
As Reported
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	15,478	19,175
Other comprehensive income (loss)		(1,605)
Effect of Adoption
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(277)	(1,704)
Other comprehensive income (loss)		603
Net Unrealized Gains (Losses) on Investments with an Allowance for Credit Losses
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(7)	(2)
Other comprehensive income (loss) before reclassifications, after tax	(8)	(4)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax
Other comprehensive income (loss)	(8)	(4)
Amounts attributable to noncontrolling interests	1
Balance at end of period	(14)	(6)
Other comprehensive income (loss) before reclassifications, tax	2	1
Reclassification from AOCI, current period, tax	0	0
Net Unrealized Gains (Losses) on Investments with an Allowance for Credit Losses | Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting standards			$ 0	$ 0
Net Unrealized Gains (Losses) on Investments with an Allowance for Credit Losses | As Reported
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(7)	(2)
Net Unrealized Gains (Losses) on Other Investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(2,469)	3,009
Other comprehensive income (loss) before reclassifications, after tax	652	(2,644)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	18	1
Other comprehensive income (loss)	670	(2,643)
Amounts attributable to noncontrolling interests	(68)	275
Balance at end of period	(1,867)	641
Other comprehensive income (loss) before reclassifications, tax	(176)	699
Reclassification from AOCI, current period, tax	(4)	(1)
Net Unrealized Gains (Losses) on Other Investments | Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting standards			0	617
Net Unrealized Gains (Losses) on Other Investments | As Reported
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(2,469)	930
Net Unrealized Gains (Losses) on Other Investments | Effect of Adoption
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period		2,079
Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	14	(6)
Other comprehensive income (loss) before reclassifications, after tax	(2)	15
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax		3
Other comprehensive income (loss)	(2)	18
Amounts attributable to noncontrolling interests
Balance at end of period	12	12
Other comprehensive income (loss) before reclassifications, tax	1	(2)
Reclassification from AOCI, current period, tax	0	(1)
Unrealized Gains (Losses) on Cash Flow Hedges | Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting standards			0	0
Unrealized Gains (Losses) on Cash Flow Hedges | As Reported
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	14	(6)
Pension and Postretirement Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(622)	(636)
Other comprehensive income (loss) before reclassifications, after tax		2
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax	9	5
Other comprehensive income (loss)	9	7
Amounts attributable to noncontrolling interests	(1)	(1)
Balance at end of period	(614)	(630)
Other comprehensive income (loss) before reclassifications, tax	0	(2)
Reclassification from AOCI, current period, tax	(2)	(2)
Pension and Postretirement Benefits | Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting standards			0	0
Pension and Postretirement Benefits | As Reported
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(622)	(636)
Cumulative impact of changes in discount rates used to measure long duration contracts
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(36)	(3,585)
Other comprehensive income (loss) before reclassifications, after tax	(396)	1,635
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax
Other comprehensive income (loss)	(396)	1,635
Amounts attributable to noncontrolling interests	39	(169)
Balance at end of period	(393)	(2,119)
Other comprehensive income (loss) before reclassifications, tax	105	(435)
Reclassification from AOCI, current period, tax	0	0
Cumulative impact of changes in discount rates used to measure long duration contracts | Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting standards			11	(1,063)
Cumulative impact of changes in discount rates used to measure long duration contracts | As Reported
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	0	0
Cumulative impact of changes in discount rates used to measure long duration contracts | Effect of Adoption
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(36)	(3,585)
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(200)	(100)
Other comprehensive income (loss) before reclassifications, after tax	16	(15)
Reclassification of (gains) losses from accumulated other comprehensive loss, after tax
Other comprehensive income (loss)	16	(15)
Amounts attributable to noncontrolling interests	(2)	1
Balance at end of period	(186)	(114)
Other comprehensive income (loss) before reclassifications, tax	0	0
Reclassification from AOCI, current period, tax	0	0
Foreign Currency Translation | Cumulative Effect, Period of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting standards			$ 0	$ 0
Foreign Currency Translation | As Reported
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(200)	(100)
Total Accumulated Other Comprehensive Income (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(3,320)	(1,320)
Balance at end of period	(3,062)	(2,216)
Total Accumulated Other Comprehensive Income (Loss) | As Reported
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(3,284)	186
Total Accumulated Other Comprehensive Income (Loss) | Effect of Adoption
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ (36)	$ (1,506)