Business Dispositions and Discontinued Operations - Additional Information (Details) - USD ($)			3 Months Ended		12 Months Ended
	Jan. 01, 2018	Dec. 03, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on discontinued operations			$ (62,000,000)	$ 0
OCI, before Reclassifications			(920,000,000)	157,000,000
Discontinued Operations, Held-for-sale | Run-Off Life and Annuity Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash proceeds from sale of business		$ 1,400,000,000.0
Dividends paid		$ 300,000,000
Ownership interest retained, percentage		970.00%
Ownership interest retained		$ 164,000,000
Reduction in long term debt		142,000,000	142,000,000		$ 142,000,000
Consideration received		$ 1,500,000,000
Loss on discontinued operations			3,200,000,000		3,300,000,000
Discontinued Operation, Amount of Adjustment to Prior Period Gain (Loss) on Disposal, Net of Tax			62,000,000	0
Adjustments to AOCI			900,000,000		$ 1,000,000,000
Management agreement term		5 years
Discontinued Operations, Held-for-sale | Run-Off Life and Annuity Business | Minimum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition services agreement term		12 months
Discontinued Operations, Held-for-sale | Run-Off Life and Annuity Business | Maximum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition services agreement term		24 months
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Tax Cuts and Jobs Act of 2017, Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax			0
Net Unrealized Gain on Securities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
OCI, before Reclassifications	$ 83,000,000		$ (882,000,000)	$ 160,000,000
Net Unrealized Gain on Securities | Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
OCI, before Reclassifications	$ 10,000,000