Changes in and Reclassifications from Accumulated Other Comprehensive Income AOCI Rollforward (Details) - USD ($) $ in Millions		3 Months Ended		4 Months Ended	5 Months Ended	9 Months Ended
	Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	May 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Jun. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net Income (Loss)		$ 67	$ 83	$ 124	$ 94		$ 270
Income before income taxes		54	71	125	101		302
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		1,769	7,715	1,769	5,810	$ 1,769	7,715		$ 1,767	$ 6,680
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent		(49)	32		(430)		238
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent		0	(7)		(18)		(16)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax		0	0		1		0
OCI, net of tax		(49)	25	(122)	(447)		222
Ending Balance		1,769	7,715	1,769	5,810	1,769	7,715		1,767	6,680
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings						193
Income Tax Expense (Benefit)		(13)	(12)	1	7		32
Net Investment Income		216	324	281	520		958
Cash Flow Hedging | Interest rate swaps | Reclassification out of Accumulated Other Comprehensive Income | Investment Income [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		0
Cash Flow Hedging | Interest rate swaps | Reclassification out of Accumulated Other Comprehensive Income | Net realized capital gain/(loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		0
Cash Flow Hedging | Currency Swap [Member] | Reclassification out of Accumulated Other Comprehensive Income | Net realized capital gain/(loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		0
Designated as Hedging Instrument | Cash Flow Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		0	10
Designated as Hedging Instrument | Cash Flow Hedging | Reclassification out of Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		0	10	0	6		28
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		(124)	931	(124)	774	(124)	931	$ (75)	0	1,022	$ 899	$ 693
Cumulative effect of accounting change										182
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance										1,204
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax					(432)		291
OCI, before Reclassifications	$ 11	(50)	45	(125)
Amounts reclassified from AOCI		1	(13)	1	(2)		(53)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent				(124)
OCI, net of tax			32		(430)		238
Ending Balance		(124)	931	(124)	774	(124)	931	(75)	0	1,022	899	693
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net Income (Loss)				(1)	(2)		53
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		(1)	20
Income before income taxes				(1)	(2)		81
Gain (Loss) on Investments, Excluding Other than Temporary Impairments		(1)	20	(1)	(2)		81
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Income Tax Expense (Benefit)		0	7	0	0		28
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income | Net realized capital gain/(loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Gain (Loss) on Investments, Excluding Other than Temporary Impairments		(1)	20
Net gains on cash flow hedging instruments
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		0	16	0	(14)	0	16	0	0	4	23	32
Cumulative effect of accounting change										0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance										4
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax					(13)		2
OCI, before Reclassifications		0	(1)	0
Amounts reclassified from AOCI		0	(6)	0	5		(18)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent				0
OCI, net of tax		0	(7)		(18)		(16)
Ending Balance		0	16	0	(14)	0	16	0	0	4	23	32
Net gains on cash flow hedging instruments | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net Income (Loss)				0	5		18
Income before income taxes				0	6		28
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Income Tax Expense (Benefit)				0	1		10
Net gains on cash flow hedging instruments | Interest rate swaps | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Gain (Loss) on Investments, Excluding Other than Temporary Impairments				0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Investment Income				0	8
Net gains on cash flow hedging instruments | Cash Flow Hedging | Reclassification out of Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Income Tax Expense (Benefit)		0	4
Net gains on cash flow hedging instruments | Cash Flow Hedging | Currency Swap [Member] | Net realized capital gain/(loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		0		0	(2)		9
Net gains on cash flow hedging instruments | Cash Flow Hedging | Currency Swap [Member] | Reclassification out of Accumulated Other Comprehensive Income | Net realized capital gain/(loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net			3	0
Net gains on cash flow hedging instruments | Designated as Hedging Instrument | Cash Flow Hedging | Interest rate swaps | Reclassification out of Accumulated Other Comprehensive Income | Investment Income [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		0	7	0	8		20
Net gains on cash flow hedging instruments | Designated as Hedging Instrument | Cash Flow Hedging | Interest rate swaps | Reclassification out of Accumulated Other Comprehensive Income | Net realized capital gain/(loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		0	0	0	0		(1)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		2	(3)	2	(2)	2	(3)	2	0	(3)	(3)	(3)
Cumulative effect of accounting change										0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance										(3)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax					1		0
OCI, before Reclassifications		0	0	2
Amounts reclassified from AOCI		0	0	0	0		0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax				2
OCI, net of tax			0		1		0
Ending Balance		2	(3)	2	(2)	2	(3)	2	0	(3)	(3)	(3)
AOCI, net of tax
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		(122)	944	(122)	758	(122)	944	(73)	0	1,023	919	722
Cumulative effect of accounting change		0	0	0	182	0	0			182
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance									0	1,205		722
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax					(444)		293
OCI, before Reclassifications		(50)	44	(123)
Amounts reclassified from AOCI		(1)	(19)	(1)	3		(71)
OCI, net of tax			25		(447)		222
Ending Balance		$ (122)	$ 944	$ (122)	$ 758	$ (122)	$ 944	$ (73)	$ 0	$ 1,023	$ 919	$ 722