Investments - Gross Unrealized losses by Major Security (Detail) $ in Millions	Jun. 30, 2025 USD ($) security	Dec. 31, 2024 USD ($) security	Jun. 30, 2024 USD ($) security
Number of Securities
Total \| security	768	1,073	1,257
Less than 12 Months \| security	157	342	301
12 Months or Greater \| security	611	731	956
Fair Value
Total	$ 21,390	$ 53,784	$ 48,227
Less than 12 Months	5,447	35,528	18,660
12 Months or Greater	15,943	18,256	29,567
Unrealized Losses
Total	(999)	(1,935)	(2,267)
Less than 12 Months	(33)	(485)	(135)
12 Months or Greater	$ (966)	$ (1,450)	$ (2,132)
U.S. government obligations
Number of Securities
Total \| security	73	113	117
Less than 12 Months \| security	9	39	17
12 Months or Greater \| security	64	74	100
Fair Value
Total	$ 10,463	$ 38,782	$ 29,776
Less than 12 Months	2,878	30,257	12,936
12 Months or Greater	7,585	8,525	16,840
Unrealized Losses
Total	(472)	(1,151)	(1,229)
Less than 12 Months	(20)	(418)	(110)
12 Months or Greater	$ (452)	$ (733)	$ (1,119)
State and local government obligations
Number of Securities
Total \| security	275	379	336
Less than 12 Months \| security	53	127	58
12 Months or Greater \| security	222	252	278
Fair Value
Total	$ 1,677	$ 2,339	$ 2,079
Less than 12 Months	289	783	411
12 Months or Greater	1,388	1,556	1,668
Unrealized Losses
Total	(78)	(117)	(144)
Less than 12 Months	(1)	(6)	(2)
12 Months or Greater	$ (77)	$ (111)	$ (142)
Foreign government obligations
Number of Securities
Total \| security			1
Less than 12 Months \| security			0
12 Months or Greater \| security			1
Fair Value
Total			$ 16
Less than 12 Months			0
12 Months or Greater			16
Unrealized Losses
Total			(1)
Less than 12 Months			0
12 Months or Greater			$ (1)
Corporate and other debt securities
Number of Securities
Total \| security	159	304	405
Less than 12 Months \| security	28	122	150
12 Months or Greater \| security	131	182	255
Fair Value
Total	$ 3,737	$ 7,034	$ 9,032
Less than 12 Months	610	2,935	3,307
12 Months or Greater	3,127	4,099	5,725
Unrealized Losses
Total	(112)	(215)	(306)
Less than 12 Months	(6)	(33)	(19)
12 Months or Greater	$ (106)	$ (182)	$ (287)
Residential mortgage-backed securities
Number of Securities
Total \| security	29	40	39
Less than 12 Months \| security	11	12	7
12 Months or Greater \| security	18	28	32
Fair Value
Total	$ 385	$ 428	$ 308
Less than 12 Months	342	377	244
12 Months or Greater	43	51	64
Unrealized Losses
Total	(7)	(11)	(9)
Less than 12 Months	(2)	(4)	0
12 Months or Greater	$ (5)	$ (7)	$ (9)
Commercial mortgage-backed securities
Number of Securities
Total \| security	153	153	183
Less than 12 Months \| security	16	8	7
12 Months or Greater \| security	137	145	176
Fair Value
Total	$ 3,331	$ 3,294	$ 3,883
Less than 12 Months	448	264	315
12 Months or Greater	2,883	3,030	3,568
Unrealized Losses
Total	(286)	(376)	(489)
Less than 12 Months	(2)	(16)	(1)
12 Months or Greater	$ (284)	$ (360)	$ (488)
Other asset-backed securities
Number of Securities
Total \| security	79	84	176
Less than 12 Months \| security	40	34	62
12 Months or Greater \| security	39	50	114
Fair Value
Total	$ 1,797	$ 1,907	$ 3,133
Less than 12 Months	880	912	1,447
12 Months or Greater	917	995	1,686
Unrealized Losses
Total	(44)	(65)	(89)
Less than 12 Months	(2)	(8)	(3)
12 Months or Greater	$ (42)	$ (57)	$ (86)

PROGRESSIVE CORP/OH/ 10-Q