Claims Development - Homeowner (Details) reported_claim in Thousands, $ in Millions	Dec. 31, 2022 USD ($) reported_claim	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	$ 3,312
Liabilities for loss and ALAE, net of reinsurance	7,967
Home Owner Line | Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	2,275
Cumulative paid losses and ALAE, net of reinsurance	1,952
All outstanding liabilities before, net of reinsurance	6
Liabilities for loss and ALAE, net of reinsurance	329
2018 | Home Owner Line | Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	386	$ 388	$ 387	$ 386	$ 370
Total of incurred but not reported liabilities plus expected development on reported losses	$ 1
Cumulative number of reported claims | reported_claim	24
Cumulative paid losses and ALAE, net of reinsurance	$ 384	381	378	368	$ 268
2019 | Home Owner Line | Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	418	422	421	432
Total of incurred but not reported liabilities plus expected development on reported losses	$ 2
Cumulative number of reported claims | reported_claim	22
Cumulative paid losses and ALAE, net of reinsurance	$ 411	407	391	$ 303
2020 | Home Owner Line | Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	470	475	497
Total of incurred but not reported liabilities plus expected development on reported losses	$ 7
Cumulative number of reported claims | reported_claim	23
Cumulative paid losses and ALAE, net of reinsurance	$ 453	434	$ 326
2021 | Home Owner Line | Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	449	495
Total of incurred but not reported liabilities plus expected development on reported losses	$ 15
Cumulative number of reported claims | reported_claim	19
Cumulative paid losses and ALAE, net of reinsurance	$ 405	$ 285
2022 | Home Owner Line | Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	552
Total of incurred but not reported liabilities plus expected development on reported losses	$ 120
Cumulative number of reported claims | reported_claim	17
Cumulative paid losses and ALAE, net of reinsurance	$ 299