Investments (Mortgage Loans Allowance for Credit Loss Rollforward by Portfolio Segment) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance, beginning of period	$ 590	$ 353
Provision (release)	(49)	36
Adoption of new credit loss guidance	0	78
Charge-offs, net of recoveries	(13)	(3)
Balance, end of period	528	464
Commercial Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance, beginning of period	252	246
Provision (release)	(5)	15
Adoption of new credit loss guidance	0	(118)
Charge-offs, net of recoveries	0	0
Balance, end of period	247	143
Residential Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance, beginning of period	232	55
Provision (release)	(30)	24
Adoption of new credit loss guidance	0	161
Charge-offs, net of recoveries	0	(3)
Balance, end of period	202	237
Agricultural Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance, beginning of period	106	52
Provision (release)	(14)	(3)
Adoption of new credit loss guidance	0	35
Charge-offs, net of recoveries	(13)	0
Balance, end of period	$ 79	$ 84