Reserves for Unpaid Losses and Loss Adjustment Expenses Level 4 Discounted Reserves, Group (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Group Insurance Policies [Member]
Weighted Average Discount Rate [Line Items]
Short-duration Insurance Contracts, Discounted Liabilities, Aggregate Discount	$ 1,303	$ 1,382	$ 1,502
Short-Duration Contracts, Discounted Liabilities, Amount	$ 5,079	$ 5,183	$ 5,339
Weighted Average Discount Rate, Percent	4.30%	4.40%	4.50%
Minimum [Member] \| Group Insurance Policies [Member]
Weighted Average Discount Rate [Line Items]
Range of Discount Rates	3.00%	3.00%	3.00%
Maximum [Member] \| Group Insurance Policies [Member]
Weighted Average Discount Rate [Line Items]
Range of Discount Rates	8.00%	8.00%	8.00%
Accident and Health Insurance Product Line [Member]
Weighted Average Discount Rate [Line Items]
Weighted Average Discount Rate, Percent	3.11%	3.24%	3.50%
Accident and Health Insurance Product Line [Member] \| Group Insurance Policies [Member]
Weighted Average Discount Rate [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	$ 6,382	$ 6,565	$ 6,841
Short-duration Insurance Contracts, Discounted Liabilities, Aggregate Discount	$ 18

Range of Discount Rates

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- Definition

The carrying amount as of the balance sheet date of loss reserves carried at present value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65670685&loc=d3e14881-158438

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.N.Q1)
-URI http://asc.fasb.org/extlink&oid=27015749&loc=d3e569934-122904

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Amount of cumulative discount related to the time value of money deducted from short-duration insurance contract liabilities that are reported at present value.

+ References

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- Definition

Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts for accident years not separately presented in claim development information. Excludes unallocated claim adjustment expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=65670685&loc=SL65671311-158438

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+ References

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- Definition

The average discount rate applied to insurance contracts to determine future policy benefits to be paid to or on behalf of policyholders.

+ References

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