Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Additional Information (Textual) [Abstract]
Total rental expense	$ 70	$ 65	$ 57
Operating lease future minimum payments due in next year	64
Operating lease future minimum payments due in year two	60
Operating lease future minimum payments due in year three	51
Operating lease future minimum payments due in year four	43
Operating lease future minimum payments due in year five	36
Operating lease future minimum payments due after year five	148
Commitments to fund limited partnerships	410
Retirement and employee savings plan expense	34	30	32
Allowance for reinsurance recoverables [Member]
Allowance for reinsurance recoverables [Line Items]
Aggregate allowance for losses on reinsurance recoverables	22	25
Reinsurance recoverable write-offs	3	6
Charges for possible losses on reinsurance recoverables	$ 0	$ 4	$ 1