Liabilities for Unpaid Claims and Claims Expenses - Liability Balance Details (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Group Disability and Life, Global Supplemental Beneftits and Other Operations [Member]
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Total liability for unpaid claims and claims expenses	$ 4,917	$ 4,574
Group Disability And Life Segment [Member]
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Total liability for unpaid claims and claims expenses	4,342	4,006
Global Supplemental Benefits Segment [Member]
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Total liability for unpaid claims and claims expenses	384	353
Other Operations Segment [Member]
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Total liability for unpaid claims and claims expenses	$ 191	$ 215