Investments (Allowance for Credit Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	$ 128	$ 106	$ 106
Addition to (release of) allowance for credit losses	(6)	22	1
Charge-offs, net of recoveries	(1)	0	(1)
Change in foreign exchange	0	0	0
Total ending balance	121	128	106
Commercial Mortgage Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	120	97	96
Addition to (release of) allowance for credit losses	(5)	23	2
Charge-offs, net of recoveries	(1)	0	(1)
Change in foreign exchange	0	0	0
Total ending balance	114	120	97
Agricultural Property Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	3	3	2
Addition to (release of) allowance for credit losses	0	0	1
Charge-offs, net of recoveries	0	0	0
Change in foreign exchange	0	0	0
Total ending balance	3	3	3
Residential property loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	0	1	2
Addition to (release of) allowance for credit losses	0	(1)	(1)
Charge-offs, net of recoveries	0	0	0
Change in foreign exchange	0	0	0
Total ending balance	0	0	1
Other collateralized loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	0	0	0
Addition to (release of) allowance for credit losses	0	0	0
Charge-offs, net of recoveries	0	0	0
Change in foreign exchange	0	0	0
Total ending balance	0	0	0
Uncollateralized loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	5	5	6
Addition to (release of) allowance for credit losses	(1)	0	(1)
Charge-offs, net of recoveries	0	0	0
Change in foreign exchange	0	0	0
Total ending balance	$ 4	$ 5	$ 5