Reinsurance (Ceded Reinsurance Receivable Assets) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 2,595	$ 2,580
Reinsurance Recoverables, Percentage of Total	100.00%	100.00%
Other Reinsurers [Member] | Customer Concentration Risk [Member] | Reinsurance Ceded Receivables Benchmark
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 176	$ 174
Reinsurance Recoverables, Percentage of Total	6.80%	6.80%
AM Best, A+ Rating [Member] | Reinsurer B [Member] | Customer Concentration Risk [Member] | Reinsurance Ceded Receivables Benchmark
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 441	$ 423
Reinsurance Recoverables, Percentage of Total	17.00%	16.40%
AM Best, A+ Rating [Member] | Reinsurer C [Member] | Customer Concentration Risk [Member] | Reinsurance Ceded Receivables Benchmark
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 216	$ 212
Reinsurance Recoverables, Percentage of Total	8.30%	8.20%
AM Best, A+ Rating [Member] | Reinsurer E [Member] | Customer Concentration Risk [Member] | Reinsurance Ceded Receivables Benchmark
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 44	$ 44
Reinsurance Recoverables, Percentage of Total	1.70%	1.70%
AM Best, A++ Rating [Member] | Reinsurer F | Customer Concentration Risk [Member] | Reinsurance Ceded Receivables Benchmark
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 42	$ 42
Reinsurance Recoverables, Percentage of Total	1.60%	1.60%
AM Best, A Rating [Member] | Reinsurer D [Member] | Customer Concentration Risk [Member] | Reinsurance Ceded Receivables Benchmark
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 59	$ 59
Reinsurance Recoverables, Percentage of Total	2.30%	2.30%
AM Best, A- Rating [Member] | Reinsurer A [Member] | Customer Concentration Risk [Member] | Reinsurance Ceded Receivables Benchmark
Ceded Credit Risk [Line Items]
Reinsurance ceded receivables	$ 1,617	$ 1,626
Reinsurance Recoverables, Percentage of Total	62.30%	63.00%