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Derivative Instruments - Derivatives - Cash Flow Hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 1		$ 4
Net realized capital gains (losses)	163	$ (30)
Net Investment Income	470	451
AOCI Attributable to Parent [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Loss on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring		0
Reclassification out of Accumulated Other Comprehensive Income \| AOCI Attributable to Parent [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Loss on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring	0
Interest rate swaps \| Reclassification out of Accumulated Other Comprehensive Income \| Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net Investment Income		8
Foreign currency swaps \| Reclassification out of Accumulated Other Comprehensive Income \| Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net Investment Income	1
Cash Flow Hedging \| Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	7	(21)
Cash Flow Hedging \| Designated as Hedging Instrument \| Reclassification out of Accumulated Other Comprehensive Income \| Net realized capital gains
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	0	1
Cash Flow Hedging \| Designated as Hedging Instrument \| 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)	1	8
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	7	(14)
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest rate swaps \| Reclassification out of Accumulated Other Comprehensive Income \| Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent \| Net realized capital gains
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	0	1
Cash Flow Hedging \| Designated as Hedging Instrument \| Interest rate swaps \| Reclassification out of Accumulated Other Comprehensive Income \| Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent \| Net investment income
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	0	8
Cash Flow Hedging \| Designated as Hedging Instrument \| Foreign currency swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)		(7)
Cash Flow Hedging \| Designated as Hedging Instrument \| Foreign currency swaps \| Reclassification out of Accumulated Other Comprehensive Income \| Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent \| Net realized capital gains
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	0	0
Cash Flow Hedging \| Designated as Hedging Instrument \| Foreign currency swaps \| Reclassification out of Accumulated Other Comprehensive Income \| Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent \| Net investment income
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	$ 1	$ 0