10-K Investments (Current And Long-Term Fixed Maturity Securities, Available-For-Sale) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	$ 31,336	$ 29,015
Gross Unrealized Gains	496	76
Gross Unrealized Losses	(1,338)	(2,378)
Fixed Maturity Securities, Allowance for Credit Loss	(4)	(9)
Available-for-sale Securities	30,490	26,704
United States Government Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	1,873	1,502
Gross Unrealized Gains	25	2
Gross Unrealized Losses	(54)	(103)
Fixed Maturity Securities, Allowance for Credit Loss	0	0
Available-for-sale Securities	1,844	1,401
Government Sponsored Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	112	82
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(3)	(5)
Fixed Maturity Securities, Allowance for Credit Loss	0	0
Available-for-sale Securities	110	78
Foreign Government Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	5	321
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(2)	(46)
Fixed Maturity Securities, Allowance for Credit Loss	0	(2)
Available-for-sale Securities	4	274
States, Municipalities And Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	3,985	4,389
Gross Unrealized Gains	69	19
Gross Unrealized Losses	(152)	(265)
Fixed Maturity Securities, Allowance for Credit Loss	0	0
Available-for-sale Securities	3,902	4,143
Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	14,838	13,721
Gross Unrealized Gains	322	31
Gross Unrealized Losses	(580)	(1,218)
Fixed Maturity Securities, Allowance for Credit Loss	(2)	(5)
Available-for-sale Securities	14,578	12,529
Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	4,071	2,978
Gross Unrealized Gains	40	9
Gross Unrealized Losses	(279)	(324)
Fixed Maturity Securities, Allowance for Credit Loss	0	0
Available-for-sale Securities	3,832	2,663
Commercial Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	2,174	2,055
Gross Unrealized Gains	13	1
Gross Unrealized Losses	(138)	(176)
Fixed Maturity Securities, Allowance for Credit Loss	(2)	(2)
Available-for-sale Securities	2,047	1,878
Other Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	4,278	3,967
Gross Unrealized Gains	25	12
Gross Unrealized Losses	(130)	(241)
Fixed Maturity Securities, Allowance for Credit Loss	0	0
Available-for-sale Securities	4,173	3,738
Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	30,490	26,704
Fixed Maturities [Member] | United States Government Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	1,844	1,401
Fixed Maturities [Member] | Government Sponsored Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	110	78
Fixed Maturities [Member] | Foreign Government Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	4	274
Fixed Maturities [Member] | States, Municipalities And Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	3,902	4,143
Fixed Maturities [Member] | Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	14,578	12,529
Fixed Maturities [Member] | Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	3,832	2,663
Fixed Maturities [Member] | Commercial Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	$ 2,047	$ 1,878