Insurance and Contractholder Liabilities - Other Segments - Activity in Liabilities for Unpaid Claims and Claims Expenses (Details) - Intenational Markets and Group Disability and Life [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability For Unpaid Claims And Claims Adjustment Expense [Line Items]
Beginning balance, unpaid claims, gross	$ 5,432	$ 5,274	$ 4,997
Less: Reinsurance and other amounts recoverable	156	140	123
Beginning balance, unpaid claims, net	5,276	5,134	4,874
Incurred claims related to:
Current year	5,616	5,350	5,097
Interest accretion	152	156	163
All other prior years	(40)	(147)	(43)
Total incurred	5,728	5,359	5,217
Paid claims related to:
Current year	3,488	3,391	3,229
Prior years	1,873	1,808	1,757
Total paid	5,361	5,199	4,986
Acquisitions	0	23	0
Foreign currency	(11)	(41)	29
Ending balance, unpaid claims, net		5,276	5,134
Add: Reinsurance and other amounts recoverable		156	140
Ending balance, unpaid claims, gross		$ 5,432	$ 5,274
Ending balance, unpaid claims and claims expense including disposal groups, net	5,632
Add: Reinsurance and other amounts recoverable, including disposal groups	184
Ending balance, unpaid claims including disposal groups, gross	$ 5,816