Changes in and Reclassifications from Accumulated Other Comprehensive Income Reclassifications from AOCI (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended	5 Months Ended	6 Months Ended
	Jun. 30, 2018	May 31, 2018	Jun. 30, 2017	May 31, 2018	Jun. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before income taxes	$ 71	$ (43)	$ 145	$ 101	$ 231
Income Tax Expense (Benefit)	14	(12)	33	7	44
Net income (loss)	57	(31)	112	94	187
Net investment income	65	208	318	520	634
Amount reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total amounts reclassified from AOCI	0	(6)	31	3	51
Amount reclassified from AOCI | Interest rate swaps | Cash Flow Hedging | Net realized capital gain/(loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Foreign currency swaps	0
Amount reclassified from AOCI | Currency Swap [Member] | Cash Flow Hedging | Net realized capital gain/(loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Foreign currency swaps	0
Accumulated Net Unrealized Investment Gain (Loss) | Amount reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net realized capital gains (losses)	0	(6)	39	(2)	60
Income before income taxes		(6)		(2)	60
Income Tax Expense (Benefit)	0	(1)	14	0	21
Net income (loss)		(5)		(2)	39
Total amounts reclassified from AOCI	0		25
Accumulated Net Unrealized Investment Gain (Loss) | Amount reclassified from AOCI | Net realized capital gain/(loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net realized capital gains (losses)	0		39
Net gains on cash flow hedging instruments | Cash Flow Hedging
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total amounts reclassified from AOCI	0		6
Net gains on cash flow hedging instruments | Currency Swap [Member] | Cash Flow Hedging | Net realized capital gain/(loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Foreign currency swaps	0	(4)		(2)	6
Net gains on cash flow hedging instruments | Amount reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before income taxes		(1)		6	18
Income Tax Expense (Benefit)		0		1	6
Net income (loss)		(1)		5	$ 12
Net gains on cash flow hedging instruments | Amount reclassified from AOCI | Cash Flow Hedging
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income Tax Expense (Benefit)	$ 0		4
Net gains on cash flow hedging instruments | Amount reclassified from AOCI | Interest rate swaps
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net realized capital gains (losses)		0		0
Net investment income		3		$ 8
Net gains on cash flow hedging instruments | Amount reclassified from AOCI | Currency Swap [Member] | Cash Flow Hedging | Net realized capital gain/(loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Foreign currency swaps		$ (4)	$ 5