Investments (Credit Quality of Agricultural and Residential Mortgage Loans) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	$ 84,344	$ 80,635
Mortgage Loans in Process of Foreclosure, Amount	103	118
Agricultural Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	3,505
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,390
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,090
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,100
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,708
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	4,241
Financing Receivable, Revolving	1,094
Mortgage Loans, Gross	$ 18,128	16,695
Loans Receivable Agricultural Mortgage Percentage	100.00%
Agricultural Mortgage Loans | Less than 65%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 3,105
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,240
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	3,005
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,047
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	2,529
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	3,687
Financing Receivable, Revolving	1,060
Mortgage Loans, Gross	$ 16,673
Loans Receivable Agricultural Mortgage Percentage	92.00%
Agricultural Mortgage Loans | 65% to 75%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 400
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	150
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	85
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	53
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	179
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	461
Financing Receivable, Revolving	34
Mortgage Loans, Gross	$ 1,362
Loans Receivable Agricultural Mortgage Percentage	7.50%
Agricultural Mortgage Loans | 76% to 80%
Accounts, Notes, Loans and Financing Receivable [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%
Accounts, Notes, Loans and Financing Receivable [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
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 614
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,401
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,033
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	482
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	339
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	8,913
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 13,782	$ 14,316
Loans Receivable Residential Mortgage Percentage	100.00%
Residential Mortgage Loans | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 606
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	2,310
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	1,007
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	473
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	331
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	8,499
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 13,226
Loans Receivable Residential Mortgage Percentage	96.00%
Residential Mortgage Loans | Nonperforming (1)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 8
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	91
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	26
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	9
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	8
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	414
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 556
Loans Receivable Residential Mortgage Percentage	4.00%