Investments (Credit Quality of Commercial Mortgage Loans) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Mortgage Loans, Gross	$ 81,393	$ 84,344
Commercial Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	4,841
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	6,079
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8,542
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	7,655
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,051
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	15,836
Financing Receivable, Revolving	2,332
Mortgage Loans, Gross	$ 51,336	$ 52,434
Loans Receivable Commercial Mortgage Percentage	100.00%
Commercial Mortgage Loans | Greater than 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 4,308
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	5,540
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8,034
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	7,492
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	5,578
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	13,817
Financing Receivable, Revolving	2,064
Mortgage Loans, Gross	$ 46,833
Loans Receivable Commercial Mortgage Percentage	91.20%
Commercial Mortgage Loans | 1.00x - 1.20x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 87
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	144
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	76
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	83
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	152
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	926
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,468
Loans Receivable Commercial Mortgage Percentage	2.90%
Commercial Mortgage Loans | Less than 1.00x
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 446
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	395
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	432
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	80
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	321
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,093
Financing Receivable, Revolving	268
Mortgage Loans, Gross	$ 3,035
Loans Receivable Commercial Mortgage Percentage	5.90%
Commercial Mortgage Loans | Less than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 3,682
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	4,536
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4,828
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	5,511
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	4,303
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	11,927
Financing Receivable, Revolving	2,332
Mortgage Loans, Gross	$ 37,119
Loans Receivable Commercial Mortgage Percentage	72.30%
Commercial Mortgage Loans | 65% to 75%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,086
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	1,507
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,375
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,065
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,108
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	2,220
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 11,361
Loans Receivable Commercial Mortgage Percentage	22.10%
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	36
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	335
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	180
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	454
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,071
Loans Receivable Commercial Mortgage Percentage	2.10%
Commercial Mortgage Loans | Greater than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 7
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	4
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	79
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	460
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,235
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,785
Loans Receivable Commercial Mortgage Percentage	3.50%