Investments - Purchase Credit Impaired (PCI) Investments (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fixed maturity securities
Contractually required payments	$ 7,761	$ 7,291
Less: Cash flows expected to be collected	(5,285)	(4,986)
Non-accretable difference	2,476	2,305
Cash flows expected to be collected	5,285	4,986
Less: Amortized cost	(3,898)	(3,673)
Accretable difference	1,387	1,313	$ 1,330
Fair value	4,029	3,647
Mortgage loans
Contractually required payments	424
Less: Cash flows expected to be collected	(286)
Non-accretable difference	138
Cash flows expected to be collected	286
Less: Amortized cost	(220)
Accretable difference	66	$ 0
Fair value	$ 221

Certain Loans Acquired in Transfer Accounted for as Available-for-sale Debt Securities, Amortized Cost

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Certain Loans Acquired in Transfer Accounted for as Available-for-sale Debt Securities, Cash Flows Expected to be Collected

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No definition available.

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Certain Loans Acquired in Transfer Accounted for as Available-for-sale Debt Securities, Nonaccretable Difference

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Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Amortized Cost

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Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Cash Flows Expected to be Collected

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Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Nonaccretable Difference

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The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and other-than-temporary impairments), for certain contractual rights to receive money on demand or on fixed or determinable dates. This relates to loans accounted for as available-for-sale debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=27045933&loc=d3e13503-111538

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The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans accounted for as available-for-sale debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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The aggregate excess of a loan's cash flows expected to be collected over the investor's initial investment in the loan for loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount of the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
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The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

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The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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