Investments (Mortgage Loans Allowance for Credit Loss Rollforward by Portfolio Segment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance, Beginning of Period	$ 353	$ 342	$ 314
Provision (release)	176	26	36
Adoption of new credit loss guidance	78	0	0
Initial credit losses on PCD loans (1)	18	0	0
Charge-offs, net of recoveries	(34)	(15)	(8)
Activity due to HFS Transfer	(1)	0	0
Allowance, Ending of Period	590	353	342
Commercial Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance, Beginning of Period	246	238	214
Provision (release)	124	8	24
Adoption of new credit loss guidance	(118)	0	0
Initial credit losses on PCD loans (1)	0	0	0
Charge-offs, net of recoveries	0	0	0
Activity due to HFS Transfer	0	0	0
Allowance, Ending of Period	252	246	238
Residential Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance, Beginning of Period	55	58	59
Provision (release)	30	7	7
Adoption of new credit loss guidance	161	0	0
Initial credit losses on PCD loans (1)	18	0	0
Charge-offs, net of recoveries	(32)	(10)	(8)
Activity due to HFS Transfer	0	0	0
Allowance, Ending of Period	232	55	58
Agricultural Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance, Beginning of Period	52	46	41
Provision (release)	22	11	5
Adoption of new credit loss guidance	35	0	0
Initial credit losses on PCD loans (1)	0	0	0
Charge-offs, net of recoveries	(2)	(5)	0
Activity due to HFS Transfer	(1)	0	0
Allowance, Ending of Period	$ 106	$ 52	$ 46