Investments Investments (Rollforward of Allowance For Credit Losses) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Available-for-sale Securities [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	$ 16	$ 33	$ 20	$ 0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment	7	42
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold	(10)	(9)
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	(1)
Corporate Debt Securities [Member] | Available-for-sale Securities [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	11	32	17	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment	2	40
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold	(8)	(8)
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	0
Debt Security, Government, Non-US [Member] | Available-for-sale Securities [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	4	1	0	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment	4	2
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold	0	(1)
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	0
Commercial Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	1	0	3	$ 0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment	1	0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold	(2)	$ 0
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	(1)
Fixed maturity securities
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	16		20
Fixed maturity securities | Corporate Debt Securities [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	11		17
Fixed maturity securities | Debt Security, Government, Non-US [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	4		0
Fixed maturity securities | Commercial Mortgage Backed Securities [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 1		$ 3