Investments (Allowance for Credit Losses and Recorded Investment) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for credit losses:
Individually evaluated for impairment	$ 7	$ 19
Collectively evaluated for impairment	114	109
Total ending balance	121	128	$ 106	$ 106
Recorded Investment:
Individually evaluated for impairment	80	104
Collectively evaluated for impairment	63,600	59,854
Total ending balance	63,680	59,958
Commercial Mortgage Loans
Allowance for credit losses:
Individually evaluated for impairment	7	19
Collectively evaluated for impairment	107	101
Total ending balance	114	120	97	96
Recorded Investment:
Individually evaluated for impairment	65	67
Collectively evaluated for impairment	59,298	55,741
Total ending balance	59,363	55,808
Agricultural Property Loans
Allowance for credit losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	3	3
Total ending balance	3	3	3	2
Recorded Investment:
Individually evaluated for impairment	15	35
Collectively evaluated for impairment	3,457	3,281
Total ending balance	3,472	3,316
Residential property loans
Allowance for credit losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	0	0
Total ending balance	0	0	1	2
Recorded Investment:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	124	157
Total ending balance	124	157
Other collateralized loans
Allowance for credit losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	0	0
Total ending balance	0	0	0	0
Recorded Investment:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	65	17
Total ending balance	65	17
Uncollateralized loans
Allowance for credit losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	4	5
Total ending balance	4	5	$ 5	$ 6
Recorded Investment:
Individually evaluated for impairment	0	2
Collectively evaluated for impairment	656	658
Total ending balance	656	660
Financial Asset Acquired with Credit Deterioration
Recorded Investment:
Financing Receivable Total	$ 0	$ 0