Liabilities for Unpaid Claims and Claims Expenses - Activity in Liabilities for Unpaid Claims and Claims Expenses (Details) - Group Disability and Life and Global Supplemental Benefits [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Beginning balance, unpaid claims, gross	$ 4,726	$ 4,359
Less: Reinsurance and other amounts recoverable	121	115
Beginning balance, unpaid claims, net	4,605	4,244
Incurred claims related to:
Current year	1,148	988
Interest accretion	43	43
All other prior years	(64)	105
Total incurred	1,127	1,136
Paid claims related to:
Current year	371	327
Prior years	691	660
Total paid	1,062	987
Foreign currency	16	5
Ending balance, unpaid claims, net	4,686	4,398
Add: Reinsurance and other amounts recoverable	123	115
Ending balance, unpaid claims, gross	$ 4,809	$ 4,513