Investments - PCI Securities Accretable Yield (Details) $ in Millions	3 Months Ended
Mar. 31, 2017 USD ($)
Fixed Maturity Securities Accretable Yield Activity
Beginning balance at January 1	$ 1,387
Purchases of PCI investments, net of sales	58
Accretion	(30)
Changes in expected cash flows	(12)
Ending balance at March 31	1,403
Mortgage Loans Accretable Yield Activity
Beginning balance at January 1	66
Purchases of PCI investments, net of sales	57
Accretion	0
Changes in expected cash flows	(10)
Ending balance at March 31	$ 113

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.

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

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

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- Definition

Current period recognition due to accretion of the 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.

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- Definition

Increases in the aggregate excess of a loan's cash flows expected to be collected over the investor's initial investment in the loan due to the acquisition of similar loans accounted for as debt securities during the period. This relates to 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
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 2: 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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- Definition

Change in the estimate of cash flows expected to be collected, after acquisition of a loan, which results in a decrease in accretable yield (for example, as a result of an other-than-temporary impairment). This relates to loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that was 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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- Definition

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.

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Amount of accretion recognized for 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.

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Amount of additions to 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.

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No definition available.

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Amount of decrease from reclassification to nonaccretable difference 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.

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