Investments (Real Estate and Real Estate Joint Ventures) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Real Estate [Line Items]
Leased real estate investments, Carrying Value	$ 4,372		$ 4,132
Other real estate investments, Carrying Value	476		461
Real estate joint ventures, Carrying Value	5,174		5,105
Real estate and real estate joint ventures	10,022		$ 9,698
Real Estate and Real Estate Joint Ventures
Real Estate [Line Items]
Gross Investment Income, Operating	130	$ 168
Leased real estate investments
Real Estate [Line Items]
Operating Lease, Lease Income	92	104
Other real estate investments
Real Estate [Line Items]
Operating Lease, Lease Income	34	33
Real estate joint ventures
Real Estate [Line Items]
Income (Loss) from Equity Method Investments	$ 4	$ 31

Amount, before investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable.

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Amount of real estate investments, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; (7) other real estate investments; (8) real estate joint ventures; and (9) unconsolidated real estate and other joint ventures not separately presented.

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The book value of investments in real estate joint ventures including direct and indirect investments.

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Amount of real estate owned for income production and capital accretion potential, not otherwise specified in the existing taxonomy. Such real estate excludes that which is occupied or used in the business, for entertainment purposes, or held in inventory for specific purposes.

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Carrying amount of income producing properties held for rental.

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