Basis of Presentation and Accounting Policies Level 4 (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings		$ 88
OCI, before Reclassifications		(920)	$ 157
Available-for-sale Securities, Equity Securities		0		$ 1,012
Fee income		323	278
Other Income		20	19
Total revenues subject to updated guidance		342	298
Operating Expense [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Distribution Costs			46
Equity Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Available-for-sale Securities, Equity Securities				$ 1,012
Net Unrealized Gain on Securities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
OCI, before Reclassifications	$ 83	(882)	160
Net Unrealized Gain on Securities | Equity Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
OCI, before Reclassifications	93
Available-for-sale Securities, Equity Securities		1,000
Discontinued Operations [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Tax Cuts and Jobs Act of 2017, Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax		0
Discontinued Operations [Member] | Net Unrealized Gain on Securities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
OCI, before Reclassifications	$ 10
Continuing Operations [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings		105
Installment billing fees [Member] | Operating Segments | Commercial Lines Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fee income		9	10
Installment billing fees [Member] | Operating Segments | Personal Lines Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fee income		10	11
Fee Income [Member] | Corporate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fee income		2	1
Insurance servicing fees [Member] | Operating Segments | Personal Lines Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other Income		19	19
Administrative services fees [Member] | Operating Segments | Group Benefits Segment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fee income		44	19
Advisor, distribution and other management fees [Member] | Asset Management Income [Member] | Operating Segments | Mutual Funds
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fee income		238	212
Other fees [Member] | Fee Income [Member] | Operating Segments | Mutual Funds
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fee income		$ 20	$ 26