Claims Development - Commercial Property (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
Commercial Property Line | Commercial Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	3,312
Cumulative paid losses and ALAE, net of reinsurance	2,774
All outstanding liabilities before, net of reinsurance	15
Liabilities for loss and ALAE, net of reinsurance	553
2018 | Commercial Property Line | Commercial Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	596	$ 597	$ 590	$ 603	$ 630
Total of incurred but not reported liabilities plus expected development on reported losses	$ 4
Cumulative number of reported claims | reported_claim	18
Cumulative paid losses and ALAE, net of reinsurance	$ 592	589	576	559	$ 386
2019 | Commercial Property Line | Commercial Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	598	600	606	621
Total of incurred but not reported liabilities plus expected development on reported losses	$ 6
Cumulative number of reported claims | reported_claim	17
Cumulative paid losses and ALAE, net of reinsurance	$ 590	579	561	$ 413
2020 | Commercial Property Line | Commercial Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	719	742	855
Total of incurred but not reported liabilities plus expected development on reported losses	$ 29
Cumulative number of reported claims | reported_claim	24
Cumulative paid losses and ALAE, net of reinsurance	$ 672	637	$ 489
2021 | Commercial Property Line | Commercial Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	586	607
Total of incurred but not reported liabilities plus expected development on reported losses	$ 15
Cumulative number of reported claims | reported_claim	14
Cumulative paid losses and ALAE, net of reinsurance	$ 527	$ 326
2022 | Commercial Property Line | Commercial Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	813
Total of incurred but not reported liabilities plus expected development on reported losses	$ 195
Cumulative number of reported claims | reported_claim	13
Cumulative paid losses and ALAE, net of reinsurance	$ 393