Business Dispositions and Discontinued Operations - Additional Information (Details) - USD ($) $ in Millions			3 Months Ended			7 Months Ended	9 Months Ended		12 Months Ended
	May 31, 2018	Jan. 01, 2018	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on discontinued operations							$ (202)	$ 0
TaxCutsAndJobsActOf2017ReclassificationFromAociToRetainedEarningsTaxEffect		$ (88)
Income (Loss) from Ongoing Equity Method Investment in Discontinued Operation after Disposal			$ 2				2
Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash proceeds from sale of business	$ 1,400
Dividends paid	$ 300
Ownership interest retained, percentage	9.70%
Ownership interest retained	$ 164
Reduction in long term debt	142								$ 142
Consideration received	$ 1,500
Loss on discontinued operations						$ 3,100			3,300
Discontinued Operation, Amount of Adjustment to Prior Period Gain (Loss) on Disposal, Net of Tax			(11)		$ 0		202	0
TaxCutsAndJobsActOf2017ReclassificationFromAociToRetainedEarningsTaxEffect				$ (193)
Adjustments to AOCI			758				758		$ 1,000
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax			$ 9		$ 77		122	$ 304
Discontinued Operations, Held-for-sale or Disposed of by Sale [Member] | Shadow DAC [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Amount of Adjustment to Prior Period Gain (Loss) on Disposal, Net of Tax							10
Operating Income (Loss) [Member] | Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Amount of Adjustment to Prior Period Gain (Loss) on Disposal, Net of Tax							104
Asset Management Income [Member] | Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Management agreement term	5 years
Other Income [Member] | Discontinued Operations, Held-for-sale or Disposed of by Sale [Member] | Maximum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Management agreement term	24 months
Equity [Member] | Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Amount of Adjustment to Prior Period Gain (Loss) on Disposal, Net of Tax				$ (193)
Deferred Tax Asset [Domain] | Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Amount of Adjustment to Prior Period Gain (Loss) on Disposal, Net of Tax							$ (141)