Investments (Credit Quality of Commercial Mortgage Loans) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage Loans, Gross	$ 83,394	$ 84,344
Commercial Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	1,258
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,372
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8,890
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	8,156
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,551
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	18,782
Financing Receivable, Revolving	2,291
Mortgage Loans, Gross	$ 52,300	$ 52,434
Loans Receivable Commercial Mortgage Percentage	100.00%
Commercial Mortgage Loans | Less than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 865
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,029
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4,745
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	5,536
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,214
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	14,215
Financing Receivable, Revolving	2,291
Mortgage Loans, Gross	$ 36,895
Loans Receivable Commercial Mortgage Percentage	70.60%
Commercial Mortgage Loans | 65% to 75%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 319
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,302
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,999
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,475
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,511
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,749
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 12,355
Loans Receivable Commercial Mortgage Percentage	23.60%
Commercial Mortgage Loans | 76% to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 66
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	33
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	135
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	66
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	404
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	547
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,251
Loans Receivable Commercial Mortgage Percentage	2.40%
Commercial Mortgage Loans | Greater than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 8
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	8
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	11
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	79
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	422
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,271
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,799
Loans Receivable Commercial Mortgage Percentage	3.40%
Commercial Mortgage Loans | Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,258
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,761
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8,365
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	8,138
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,226
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	17,051
Financing Receivable, Revolving	2,291
Mortgage Loans, Gross	$ 49,090
Loans Receivable Commercial Mortgage Percentage	93.90%
Commercial Mortgage Loans | 1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	351
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	65
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	18
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	193
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,019
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,646
Loans Receivable Commercial Mortgage Percentage	3.10%
Commercial Mortgage Loans | Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 0
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	260
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	460
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	132
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	712
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,564
Loans Receivable Commercial Mortgage Percentage	3.00%