Liabilities for Unpaid Claims and Claims Expenses - Reconciliation to the Liability for Unpaid Claims and Claims Expense (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Group Disability and Life, Global Supplemental Beneftits and Other Operations [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liability for unpaid claims and claims expenses	$ 4,917	$ 4,574
Group Disability And Life Segment [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for unpaid claims and claims expenses, net of reinsurance	4,242
Reinsurance recoverable on unpaid claims	100
Total liability for unpaid claims and claims expenses	4,342	4,006
Global Supplemental Benefits Segment [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liability for unpaid claims and claims expenses	384	353
Other Operations Segment [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liability for unpaid claims and claims expenses	191	$ 215
Long-term Disability [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for unpaid claims and claims expenses, net of reinsurance	3,622
Long-term Disability [Member] | Group Disability And Life Segment [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for unpaid claims and claims expenses, net of reinsurance	3,622
Reinsurance recoverable on unpaid claims	86
Other Short-duration Insurance Product Line [Member] | Group Disability And Life Segment [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liability for unpaid claims and claims expenses, net of reinsurance	620
Reinsurance recoverable on unpaid claims	$ 14