Fair Value (Financial Instruments Carried at Other Than Fair Value) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Assets
Policy loans	$ 1,043	$ 1,106
Liabilities
Separate account liabilities	103,801	110,156
Carrying Value
Assets
Mortgage loans	12,141	10,525
Policy loans	1,043	1,106
Real estate joint ventures		5
Other limited partnership interests		36
Premiums, reinsurance and other receivables	1,475	1,556
Liabilities
Policyholder account balances	15,724	15,626
Long-term debt	35	35
Other liabilities	475	459
Separate account liabilities	1,188	1,206
Other Investments Fair Value Disclosure	85	71
Estimated Fair Value
Assets
Mortgage loans	12,225	10,768
Policy loans	1,106	1,185
Real estate joint ventures		22
Other limited partnership interests		28
Premiums, reinsurance and other receivables	1,674	1,909
Liabilities
Policyholder account balances	14,687	15,760
Long-term debt	40	42
Other liabilities	469	461
Separate account liabilities	1,188	1,206
Other Investments Fair Value Disclosure	85	71
Estimated Fair Value \| Level 1
Assets
Mortgage loans	0	0
Policy loans	0	0
Real estate joint ventures		0
Other limited partnership interests		0
Premiums, reinsurance and other receivables	0	0
Liabilities
Policyholder account balances	0	0
Long-term debt	0	0
Other liabilities	0	0
Separate account liabilities	0	0
Other Investments Fair Value Disclosure	0	0
Estimated Fair Value \| Level 2
Assets
Mortgage loans	0	0
Policy loans	683	746
Real estate joint ventures		0
Other limited partnership interests		0
Premiums, reinsurance and other receivables	88	126
Liabilities
Policyholder account balances	0	0
Long-term debt	40	42
Other liabilities	125	93
Separate account liabilities	1,188	1,206
Other Investments Fair Value Disclosure	72	71
Estimated Fair Value \| Level 3
Assets
Mortgage loans	12,225	10,768
Policy loans	423	439
Real estate joint ventures		22
Other limited partnership interests		28
Premiums, reinsurance and other receivables	1,586	1,783
Liabilities
Policyholder account balances	14,687	15,760
Long-term debt	0	0
Other liabilities	344	368
Separate account liabilities	0	0
Other Investments Fair Value Disclosure	$ 13	$ 0

Total amount of mortgage loans not valued on a recurring basis as of the balance sheet date.

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Fair value portion of other investments not otherwise specified in the taxonomy.

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The fair value portion of investments in other limited partnership interests.

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Fair value portion of the liability of policyholders for deposits held under the terms of insurance contracts.

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Amount before allowance of loans made to policy and contract holders using their life insurance contracts' cash value or separate accounts as collateral. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums over and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Fair value portion of other liabilities.

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

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Fair value portion of receivables, including, but not limited to, trade account receivables, note receivables, and loan receivables.

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Amount of liability for variable contracts that meet specified criteria that are backed by assets held in separate accounts and carried at the fair value of those assets.

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