Investments (Summary of fixed maturity and equity securities) (Details) - USD ($) $ in Millions	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	$ 45,456		$ 44,668
Gross Unrealized Gains	883		1,089
Gross Unrealized Losses	2,396		2,286
Allowance for Credit Losses	63	$ 75	69	$ 51	$ 47	$ 45
Estimated Fair Value	43,880		43,402
Total fixed maturity securities trading	2		0
Total fixed maturity securities trading	2		0
Total fixed maturity securities	45,458		44,668
Total fixed maturity securities	43,882		43,402
Corporate and other bonds
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	25,722		25,484
Gross Unrealized Gains	513		682
Gross Unrealized Losses	964		881
Allowance for Credit Losses	16	31	28	14	15	13
Estimated Fair Value	25,255		25,257
Total fixed maturity securities	26,213		26,250
States, municipalities and political subdivisions
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	9,257		8,870
Gross Unrealized Gains	305		303
Gross Unrealized Losses	727		742
Allowance for Credit Losses	0		0
Estimated Fair Value	8,835		8,431
Total fixed maturity securities	8,835		8,431
Residential mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	4,235		4,011
Gross Unrealized Gains	31		50
Gross Unrealized Losses	385		366
Allowance for Credit Losses	0		0
Estimated Fair Value	3,881		3,695
Commercial mortgage-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	1,580		1,566
Gross Unrealized Gains	12		18
Gross Unrealized Losses	79		80
Allowance for Credit Losses	21		21
Estimated Fair Value	1,492		1,483
Other asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	3,690		3,729
Gross Unrealized Gains	14		28
Gross Unrealized Losses	217		194
Allowance for Credit Losses	26		20
Estimated Fair Value	3,461		3,543
Asset-backed
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	9,505		9,306
Gross Unrealized Gains	57		96
Gross Unrealized Losses	681		640
Allowance for Credit Losses	47	$ 44	41	$ 37	$ 32	$ 32
Estimated Fair Value	8,834		8,721
Total fixed maturity securities	8,834		8,721
U.S. Treasury and obligations of government-sponsored enterprises
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	242		236
Gross Unrealized Gains	0		1
Gross Unrealized Losses	3		3
Allowance for Credit Losses	0		0
Estimated Fair Value	239		234
Foreign government
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	722		764
Gross Unrealized Gains	8		7
Gross Unrealized Losses	21		20
Allowance for Credit Losses	0		0
Estimated Fair Value	709		751
Redeemable preferred stock
Fixed maturity securities available-for-sale:
Cost or Amortized Cost	8		8
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Allowance for Credit Losses	0		0
Estimated Fair Value	$ 8		$ 8