Claim and Claim Adjustment Expense Reserves - Impact of Loss Portfolio Transfer on the Consolidated Statement of Operations (Details) - Loss Portfolio Transfer - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Net A&EP adverse development before consideration of LPT	$ 0	$ 0	$ 60	$ 200
Retroactive reinsurance benefit recognized	(17)	(12)	(60)	(94)
Pretax impact of A&EP reserve development and the LPT	$ (17)	$ (12)	$ 0	$ 106