Accumulated Other Comprehensive Income (Loss) by Component (Schedule of Accumulated Other Comprehensive Income (Loss) by Component) (Details) - USD ($) $ in Millions						3 Months Ended
		Dec. 31, 2022		Dec. 31, 2021		Mar. 31, 2023	Mar. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	[1]					$ 8,548
Other comprehensive income (loss) before reclassifications						265	$ (1,027)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax						(25)	(7)
Other comprehensive income (loss) after tax (expense) benefit						290	(1,020)
Total stockholder's equity at end of period		$ 8,548	[1]			8,667	9,698	[2]
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle		11		$ (446)
Reclassification from AOCI, tax						6	3
Tax (expense) benefit on other comprehensive income (loss)						(75)	262
Prior to Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						8,825
Total stockholder's equity at end of period		8,825
Effect of Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(277)
Total stockholder's equity at end of period		(277)
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(3,598)	(1,360)	[2]
Total stockholder's equity at end of period		(3,598)		(1,360)	[2]	(3,308)	(2,380)	[2]
Accumulated other comprehensive income (loss) | Prior to Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(3,557)	320	[2]
Total stockholder's equity at end of period		(3,557)		320	[2]
Accumulated other comprehensive income (loss) | Effect of Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(41)	(1,680)	[2]
Total stockholder's equity at end of period		(41)		(1,680)	[2]
Net unrealized gains (losses) on investments | Net unrealized gains (losses) on investments with an allowance for credit losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(7)	(2)
Other comprehensive income (loss) before reclassifications						(8)	(4)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax						0	0
Other comprehensive income (loss) after tax (expense) benefit						(8)	(4)
Total stockholder's equity at end of period		(7)		(2)		(15)	(6)
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle		0		0
Reclassification from AOCI, tax						0	0
Tax (expense) benefit on other comprehensive income (loss)						2	1
Net unrealized gains (losses) on investments | Net unrealized gains (losses) on investments with an allowance for credit losses | Prior to Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(7)	(2)
Total stockholder's equity at end of period		(7)		(2)
Net unrealized gains (losses) on investments | Net unrealized gains (losses) on investments with an allowance for credit losses | Effect of Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						0	0
Total stockholder's equity at end of period		0		0
Net unrealized gains (losses) on investments | Net unrealized gains (losses) on other investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(2,738)	3,359
Other comprehensive income (loss) before reclassifications						652	(2,644)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax						(18)	(1)
Other comprehensive income (loss) after tax (expense) benefit						670	(2,643)
Total stockholder's equity at end of period		(2,738)		3,359		(2,068)	716
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle		0		617
Reclassification from AOCI, tax						4	1
Tax (expense) benefit on other comprehensive income (loss)						(180)	698
Net unrealized gains (losses) on investments | Net unrealized gains (losses) on other investments | Prior to Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(2,738)	1,039
Total stockholder's equity at end of period		(2,738)		1,039
Net unrealized gains (losses) on investments | Net unrealized gains (losses) on other investments | Effect of Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						0	2,320
Total stockholder's equity at end of period		0		2,320
Pension and postretirement benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(591)	(604)
Other comprehensive income (loss) before reclassifications						0	0
Amounts reclassified from accumulated other comprehensive income (loss) net of tax						(7)	(6)
Other comprehensive income (loss) after tax (expense) benefit						7	6
Total stockholder's equity at end of period		(591)		(604)		(584)	(598)
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle		0		0
Reclassification from AOCI, tax						2	2
Tax (expense) benefit on other comprehensive income (loss)						(2)	(2)
Pension and postretirement benefits | Prior to Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(591)	(604)
Total stockholder's equity at end of period		(591)		(604)
Pension and postretirement benefits | Effect of Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						0	0
Total stockholder's equity at end of period		0		0
Cumulative impact of changes in discount rates used to measure long duration contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(41)	(4,000)
Other comprehensive income (loss) before reclassifications						(396)	1,635
Amounts reclassified from accumulated other comprehensive income (loss) net of tax						0	0
Other comprehensive income (loss) after tax (expense) benefit						(396)	1,635
Total stockholder's equity at end of period		(41)		(4,000)		(437)	(2,365)
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle		11		(1,063)
Reclassification from AOCI, tax						0	0
Tax (expense) benefit on other comprehensive income (loss)						105	(435)
Cumulative impact of changes in discount rates used to measure long duration contracts | Prior to Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						0	0
Total stockholder's equity at end of period		0		0
Cumulative impact of changes in discount rates used to measure long duration contracts | Effect of Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(41)	(4,000)
Total stockholder's equity at end of period		(41)		(4,000)
Cumulative foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(221)	(113)
Other comprehensive income (loss) before reclassifications						17	(14)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax						0	0
Other comprehensive income (loss) after tax (expense) benefit						17	(14)
Total stockholder's equity at end of period		(221)		(113)		(204)	(127)
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle		0		0
Reclassification from AOCI, tax						0	0
Tax (expense) benefit on other comprehensive income (loss)						0	0
Cumulative foreign currency translation adjustment | Prior to Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						(221)	(113)
Total stockholder's equity at end of period		(221)		(113)
Cumulative foreign currency translation adjustment | Effect of Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period						$ 0	$ 0
Total stockholder's equity at end of period		$ 0		$ 0

[1] As of January 1, 2023, the Company adopted ASU 2018-12 using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been adjusted to reflect application of the new guidance. See Note A to the Condensed Consolidated Financial Statements for additional information.

[2] As of January 1, 2023, the Company adopted ASU 2018-12 using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been adjusted to reflect application of the new guidance. See Note A to the Condensed Consolidated Financial Statements for additional information.