Derivatives - Cash Flow Hedges (Details) - Designated as Hedging Instrument - Cash Flow Hedging - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	$ (6)	$ 1	$ 25
Reclassification out of Accumulated Other Comprehensive Income
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	42	47	36
Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	8	0	25
Interest rate swaps \| Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent \| Reclassification out of Accumulated Other Comprehensive Income \| Net realized capital gain/(loss)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	5	10	5
Interest rate swaps \| Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent \| Reclassification out of Accumulated Other Comprehensive Income \| Net investment income
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	37	37	31
Foreign currency swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	$ (14)	$ 1	$ 0

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- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624177-113959

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

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