Investments (Credit Quality of Agricultural and Residential 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
Mortgage Loans in Process of Foreclosure, Amount	94	103
Agricultural Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	654
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	3,508
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,346
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,986
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,061
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	6,483
Financing Receivable, Revolving	1,013
Mortgage Loans, Gross	$ 18,051	18,128
Loans Receivable Agricultural Mortgage Percentage	100.00%
Agricultural Mortgage Loans | Less than 65%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 431
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	3,119
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,174
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	2,903
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	1,008
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	5,800
Financing Receivable, Revolving	910
Mortgage Loans, Gross	$ 16,345
Loans Receivable Agricultural Mortgage Percentage	90.60%
Agricultural Mortgage Loans | 65% to 75%
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 223
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	389
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	172
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	83
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	53
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	590
Financing Receivable, Revolving	103
Mortgage Loans, Gross	$ 1,613
Loans Receivable Agricultural Mortgage Percentage	8.90%
Agricultural Mortgage Loans | 76% to 80%
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	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	51
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 51
Loans Receivable Agricultural Mortgage Percentage	0.30%
Agricultural Mortgage Loans | Greater than 80%
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	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	42
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 42
Loans Receivable Agricultural Mortgage Percentage	0.20%
Residential Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 40
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	605
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,204
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	921
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	455
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	8,818
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 13,043	$ 13,782
Loans Receivable Residential Mortgage Percentage	100.00%
Residential Mortgage Loans | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 40
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	599
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,153
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	906
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	445
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	8,371
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 12,514
Loans Receivable Residential Mortgage Percentage	95.90%
Residential Mortgage Loans | Nonperforming
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	6
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	51
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	15
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	10
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	447
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 529
Loans Receivable Residential Mortgage Percentage	4.10%