Investments (Narrative) (Details) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2021 USD ($) security loan item	Dec. 31, 2020 USD ($) security loan item
Investments [Line Items]
Increase (decrease) in gross AFS securities unrealized losses	$ 605
Number of partnerships in alternative investment portfolio \| item	279	271
Alternative investments as a percentage of overall invested assets	1.00%	1.00%
Amortized cost	$ 105,866	$ 104,174
Fair Value	117,313	123,044
Fair value of collateral received that we are permitted to sell or re-pledge	21
Investment commitments	2,000
Investment commitments for limited partnerships	1,100
Investment commitments for mortgage loans on real estate	420
Investment commitments for private placements	$ 413
Minimum [Member]
Investments [Line Items]
Percentage of the fair value of securities obtained as collateral under reverse repurchase agreements	80.00%
Maximum [Member]
Investments [Line Items]
Percentage of the fair value of securities obtained as collateral under reverse repurchase agreements	95.00%
Federal Home Loan Mortgage Corporation [Member] \| Investments [Member]
Investments [Line Items]
Fair value	$ 1,200	1,200
Federal National Mortgage Association [Member] \| Investments [Member]
Investments [Line Items]
Fair value	1,100	1,000
Consumer Non-Cyclical Industry [Member] \| Investments [Member]
Investments [Line Items]
Fair value	19,000	20,300
Financial Service [Member] \| Investments [Member]
Investments [Line Items]
Fair value	$ 18,500	$ 19,600
Corporate Bonds [Member]
Investments [Line Items]
Percentage of fair value rated as investment grade	96.00%	96.00%
Corporate Bonds [Member] \| External Credit Rating, Non Investment Grade [Member]
Investments [Line Items]
Amortized cost	$ 4,000	$ 4,100
Fair Value	$ 4,100	$ 4,200
Federal National Mortgage Association [Member] \| Federal Home Loan Mortgage Corporation [Member] \| Investments [Member]
Investments [Line Items]
Concentration risk, percentage	1.00%	1.00%
Federal National Mortgage Association [Member] \| Federal National Mortgage Association [Member] \| Investments [Member]
Investments [Line Items]
Concentration risk, percentage	1.00%	1.00%
Federal National Mortgage Association [Member] \| Consumer Non-Cyclical Industry [Member] \| Investments [Member]
Investments [Line Items]
Concentration risk, percentage		13.00%
Federal National Mortgage Association [Member] \| Financial Service [Member] \| Investments [Member]
Investments [Line Items]
Concentration risk, percentage	12.00%	13.00%
Commercial [Member]
Investments [Line Items]
Number of impaired loans \| security	9	4
Impaired financing receivable, principal balance	$ 3	$ 1
Commercial [Member] \| Federal National Mortgage Association [Member] \| Geographic Concentration Risk [Member] \| Mortgage Loans On Real Estate [Member] \| California [Member]
Investments [Line Items]
Concentration risk, percentage	25.00%	24.00%
Commercial [Member] \| Federal National Mortgage Association [Member] \| Geographic Concentration Risk [Member] \| Mortgage Loans On Real Estate [Member] \| Texas [Member]
Investments [Line Items]
Concentration risk, percentage	10.00%	10.00%
Residential [Member]
Investments [Line Items]
Number of loans past due \| loan	113	147
Number of impaired loans \| security	74	76
Impaired financing receivable, principal balance	$ 34	$ 34
Residential [Member] \| Federal National Mortgage Association [Member] \| Geographic Concentration Risk [Member] \| Mortgage Loans On Real Estate [Member] \| California [Member]
Investments [Line Items]
Concentration risk, percentage	28.00%	32.00%
Residential [Member] \| Federal National Mortgage Association [Member] \| Geographic Concentration Risk [Member] \| Mortgage Loans On Real Estate [Member] \| Florida [Member]
Investments [Line Items]
Concentration risk, percentage	19.00%	18.00%

Alternative investments as a percentage of overall invested assets.

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This item represents the change in gross unrealized holding gain or loss on available-for-sale securities that has been included in accumulated other comprehensive income, a separate component of shareholders' equity, during the period.

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Percentage of the fair value of portfolio that was rated investment grade as of balance sheet date.

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Financing receivable, Number of loans past due

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Investments [Line Items]

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Number of partnerships represented in alternative investment portfolio.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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This item represents disclosure of all significant concentrations of credit risk or market risk arising from the subject financial instrument (as defined), whether from an individual counterparty or groups of counterparties.

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Fair value of collateral permitted, by contact or custom, to be sold or re-pledged.

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Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.

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