Changes in and Reclassifications from Accumulated Other Comprehensive Income Reclassifications from AOCI (Details) - USD ($) $ in Millions	3 Months Ended		4 Months Ended	5 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	May 31, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before income taxes	$ 54	$ 71	$ 125	$ 101	$ 302
Income Tax Expense (Benefit)	(13)	(12)	1	7	32
Net income (loss)	67	83	124	94	270
Net investment income	216	324	281	520	958
Amount reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total amounts reclassified from AOCI	(1)	19	(1)	3	71
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)	(1)	20	(1)	(2)	81
Income before income taxes			(1)	(2)	81
Income Tax Expense (Benefit)	0	7	0	0	28
Net income (loss)			(1)	(2)	53
Total amounts reclassified from AOCI	(1)	13
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)	(1)	20
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		0	(2)	9
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			0	6	28
Income Tax Expense (Benefit)			0	1	10
Net income (loss)			0	5	$ 18
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			0	$ 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		$ 3	$ 0