Investments (Impaired Mortgage Loans) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		$ 17	$ 31
Impaired Financing Receivable, Recorded Investment		17	31
Impaired Financing Receivable, Related Allowance		0	0
Impaired Financing Receivable Net Of Related Allowance		17	31
Impaired Financing Receivable, Average Recorded Investment	[1]	20	24		$ 4
Impaired Financing Receivable, Interest Income, Accrual Method		1	1		0
Impaired mortgage loans with no valuation allowance recorded
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		17	31
Impaired Financing Receivable, Recorded Investment		17	31
Impaired Financing Receivable, Related Allowance		0	0
Impaired Financing Receivable Net Of Related Allowance		17	31
Impaired Financing Receivable, Average Recorded Investment		20	24	[1]	4	[1]
Impaired Financing Receivable, Interest Income, Accrual Method		1	1		0
Impaired mortgage loans with valuation allowance recorded
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		0	0
Impaired Financing Receivable, Recorded Investment		0	0
Impaired Financing Receivable, Related Allowance		0	0
Impaired Financing Receivable Net Of Related Allowance		0	0
Impaired Financing Receivable, Average Recorded Investment		0	0	[1]	0	[1]
Impaired Financing Receivable, Interest Income, Accrual Method		$ 0	$ 0		$ 0

[1] Average recorded investment represents the average loan balances as of the beginning of period and all subsequent quarterly end of period balances.