Investments (Credit Quality of Commercial Mortgage Loans) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	$ 80,635	$ 75,795
Loans Receivable Commercial Mortgage Percentage	100.00%	100.00%
Fair Value Mortgage loans	$ 51,340	$ 48,747
Estimated Fair Value Commercial Mortgage Percentage	100.00%	100.00%
Less than 65%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable Commercial Mortgage Percentage	82.10%	85.20%
Fair Value Mortgage loans	$ 42,330	$ 41,599
Estimated Fair Value Commercial Mortgage Percentage	82.40%	85.30%
65% to 75%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable Commercial Mortgage Percentage	15.00%	12.00%
Fair Value Mortgage loans	$ 7,589	$ 5,849
Estimated Fair Value Commercial Mortgage Percentage	14.80%	12.00%
76% to 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable Commercial Mortgage Percentage	1.60%	1.40%
Fair Value Mortgage loans	$ 805	$ 664
Estimated Fair Value Commercial Mortgage Percentage	1.60%	1.40%
Greater than 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable Commercial Mortgage Percentage	1.30%	1.40%
Fair Value Mortgage loans	$ 616	$ 635
Estimated Fair Value Commercial Mortgage Percentage	1.20%	1.30%
Commercial Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	$ 49,624	$ 48,463
Commercial Mortgage Loans | Less than 65%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	40,740	41,288
Commercial Mortgage Loans | 65% to 75%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	7,427	5,815
Commercial Mortgage Loans | 76% to 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	818	688
Commercial Mortgage Loans | Greater than 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	639	672
Commercial Mortgage Loans | Greater than 1.20x
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	46,870	47,069
Commercial Mortgage Loans | Greater than 1.20x | Less than 65%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	38,926	40,360
Commercial Mortgage Loans | Greater than 1.20x | 65% to 75%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	6,975	5,790
Commercial Mortgage Loans | Greater than 1.20x | 76% to 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	564	423
Commercial Mortgage Loans | Greater than 1.20x | Greater than 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	405	496
Commercial Mortgage Loans | 1.00x - 1.20x
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	1,500	1,212
Commercial Mortgage Loans | 1.00x - 1.20x | Less than 65%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	1,195	827
Commercial Mortgage Loans | 1.00x - 1.20x | 65% to 75%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	54	0
Commercial Mortgage Loans | 1.00x - 1.20x | 76% to 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	17	209
Commercial Mortgage Loans | 1.00x - 1.20x | Greater than 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	234	176
Commercial Mortgage Loans | Less than 1.00x
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	1,254	182
Commercial Mortgage Loans | Less than 1.00x | Less than 65%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	619	101
Commercial Mortgage Loans | Less than 1.00x | 65% to 75%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	398	25
Commercial Mortgage Loans | Less than 1.00x | 76% to 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	237	56
Commercial Mortgage Loans | Less than 1.00x | Greater than 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	$ 0	$ 0