Reinsurance - Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Effects of Reinsurance [Line Items]
Premiums receivable	$ 66	$ 59
Reinsurance recoverable	7,566	7,228
Reinsurance recoverable	7,632	7,287
Future policy benefits and contract owner account balances	58,239	57,620
Liability for funds withheld under reinsurance agreements	791	729
Total	59,030	58,349
Direct
Effects of Reinsurance [Line Items]
Premiums receivable	110	105
Reinsurance recoverable	0	0
Reinsurance recoverable	110	105
Future policy benefits and contract owner account balances	62,005	61,566
Liability for funds withheld under reinsurance agreements	791	729
Total	62,796	62,295
Assumed
Effects of Reinsurance [Line Items]
Premiums receivable	405	358
Reinsurance recoverable	0	0
Reinsurance recoverable	405	358
Future policy benefits and contract owner account balances	3,800	3,282
Liability for funds withheld under reinsurance agreements	0	0
Total	3,800	3,282
Ceded
Effects of Reinsurance [Line Items]
Premiums receivable	(449)	(404)
Reinsurance recoverable	7,566	7,228
Reinsurance recoverable	7,117	6,824
Future policy benefits and contract owner account balances	(7,566)	(7,228)
Liability for funds withheld under reinsurance agreements	0	0
Total	$ (7,566)	$ (7,228)

The liability as of the balance sheet date for future benefits to be paid to or on behalf of policyholders and expenses, less the present value of future net premiums payable under the insurance contracts and the policy cash accumulations, for the segregated group of participating or dividend-paying policies and contracts identified as a closed block.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of funds held as security for payments to be received under reinsurance contracts.

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The carrying amount as of the balance sheet date due the entity from (a) agents and insureds, (b) uncollected premiums and (c) others, net of the allowance for doubtful accounts.

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Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

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Amount before valuation allowance recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

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Reinsurance Liabilities

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