Schedule V - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Collective valuation allowance for losses, beginning of period	$ 3	$ 3	$ 3
Allowance for losses on commercial mortgage loans	0	0	0
Collective valuation allowance for losses, end of period	3	3	3
Valuation allowance on deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	964	963	972
Charged to Costs and Expenses	(311)	6	(14)
Write-offs/Payments/Other	0	(5)	5
Ending Balance	$ 653	$ 964	$ 963