Accumulated Other Comprehensive Income (Loss) by Component (Schedule of Accumulated Other Comprehensive Income (Loss) by Component) (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended		9 Months Ended			12 Months Ended
		Sep. 30, 2023	Sep. 30, 2022		Jun. 30, 2022		Sep. 30, 2023	Sep. 30, 2022		Dec. 31, 2022		Dec. 31, 2021
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		$ (351)	$ (946)				(231)	$ (2,775)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		(35)	(106)				(88)	(132)
Other comprehensive income (loss) after tax (expense) benefit		(316)	(840)				(143)	(2,643)
Total stockholder's equity at end of period		8,563	8,003	[2]			8,563	8,003	[2]	$ 8,548	[1]
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle					$ 120					11		$ 446
Reclassification from AOCI, tax		9	13				23	19
Tax (expense) benefit on other comprehensive income (loss)		72	210				39	661
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		(3,425)	(3,163)	[2]	(1,360)	[2]	(3,598)	(1,360)	[2]	(1,360)	[2]	(1,537)
Total stockholder's equity at end of period		(3,741)	(4,003)	[2]	(3,163)	[2]	(3,741)	(4,003)	[2]	(3,598)		(1,360)	[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		(3,425)	(2,713)	[2]	320	[2]	(3,557)	320	[2]	320	[2]	803
Total stockholder's equity at end of period					(2,713)	[2]				(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		0	(450)	[2]	(1,680)	[2]	(41)	(1,680)	[2]	(1,680)	[2]
Total stockholder's equity at end of period					(450)	[2]				(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		(16)	(8)		(2)		(7)	(2)		(2)
Other comprehensive income (loss) before reclassifications		(9)	0				(25)	(5)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		(8)	2				(15)	3
Other comprehensive income (loss) after tax (expense) benefit		(1)	(2)				(10)	(8)
Total stockholder's equity at end of period		(17)	(10)		(8)		(17)	(10)		(7)		(2)
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle					0					0		0
Reclassification from AOCI, tax		2	0				4	(1)
Tax (expense) benefit on other comprehensive income (loss)		1	1				3	2
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			(8)		(2)		(7)	(2)		(2)
Total stockholder's equity at end of period					(8)					(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		0	0		0
Total stockholder's equity at end of period					0					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		(2,481)	(1,510)		3,359		(2,738)	3,359		3,359
Other comprehensive income (loss) before reclassifications		(1,105)	(1,837)				(880)	(6,721)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		(21)	(102)				(53)	(117)
Other comprehensive income (loss) after tax (expense) benefit		(1,084)	(1,735)				(827)	(6,604)
Total stockholder's equity at end of period		(3,565)	(3,245)		(1,510)		(3,565)	(3,245)		(2,738)		3,359
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle					(108)					0		(617)
Reclassification from AOCI, tax		6	11				14	15
Tax (expense) benefit on other comprehensive income (loss)		289	476				221	1,764
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			(1,918)		1,039		(2,738)	1,039		1,039
Total stockholder's equity at end of period					(1,918)					(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			408		2,320		0	2,320		2,320
Total stockholder's equity at end of period					408					0		2,320
Pension and postretirement benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period		(577)	(592)		(604)		(591)	(604)		(604)
Other comprehensive income (loss) before reclassifications		0	0				0	0
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		(6)	(6)				(20)	(18)
Other comprehensive income (loss) after tax (expense) benefit		6	6				20	18
Total stockholder's equity at end of period		(571)	(586)		(592)		(571)	(586)		(591)		(604)
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle					0					0		0
Reclassification from AOCI, tax		1	2				5	5
Tax (expense) benefit on other comprehensive income (loss)		(1)	(2)				(5)	(5)
Pension and postretirement benefits | Prior to Adoption
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period			(592)		(604)		(591)	(604)		(604)
Total stockholder's equity at end of period					(592)					(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		0	0		0
Total stockholder's equity at end of period					0					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		(181)	(858)		(4,000)		(41)	(4,000)		(4,000)
Other comprehensive income (loss) before reclassifications		818	994				678	4,136
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		0	0				0	0
Other comprehensive income (loss) after tax (expense) benefit		818	994				678	4,136
Total stockholder's equity at end of period		637	136		(858)		637	136		(41)		(4,000)
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle					228					11		1,063
Reclassification from AOCI, tax		0	0				0	0
Tax (expense) benefit on other comprehensive income (loss)		(217)	(265)				(180)	(1,100)
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		0	0		0
Total stockholder's equity at end of period					0					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			(858)		(4,000)		(41)	(4,000)		(4,000)
Total stockholder's equity at end of period					(858)					(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		(170)	(195)		(113)		(221)	(113)		(113)
Other comprehensive income (loss) before reclassifications		(55)	(103)				(4)	(185)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		0	0				0	0
Other comprehensive income (loss) after tax (expense) benefit		(55)	(103)				(4)	(185)
Total stockholder's equity at end of period		(225)	(298)		(195)		(225)	(298)		(221)		(113)
Income tax effects allocated directly to equity, cumulative effect of change in accounting principle					0					0		0
Reclassification from AOCI, tax		0	0				0	0
Tax (expense) benefit on other comprehensive income (loss)		$ 0	0				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			(195)		(113)		(221)	(113)		(113)
Total stockholder's equity at end of period					(195)					(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		$ 0	$ 0		0
Total stockholder's equity at end of period					$ 0					$ 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.