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	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Balance at January 1,	$ 4,359	$ 4,178	$ 4,038
Less: Reinsurance and other amounts recoverable	115	104	99
Balance at January 1, net	4,244	4,074	3,939
Incurred claims related to:
Current year	4,258	3,813	3,512
Interest accretion	161	163	149
All other prior years	93	(91)	(165)
Total incurred	4,512	3,885	3,496
Paid claims related to:
Current year	2,575	2,325	2,078
Prior years	1,560	1,382	1,271
Total paid	4,135	3,707	3,349
Acquisitions	0	11	0
Foreign currency	(16)	(19)	(12)
Balance at December 31, net	4,605	4,244	4,074
Add: Reinsurance and other amounts recoverable	121	115	104
Balance at December 31,	$ 4,726	$ 4,359	$ 4,178