Insurance and Contractholder Liabilities - Activity in Liabilities for Unpaid Claims and Claim Expenses (Details) - Intenational Markets and Group Disability and Life - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Beginning balance	$ 5,816
Beginning balance		$ 5,432	$ 5,274
Less: Reinsurance and other amounts recoverable	184
Less: Reinsurance and other amounts recoverable		156	140
Beginning balance, net	5,632
Beginning balance, net		5,276	5,134
Incurred claims related to:
Current year	5,810	5,616	5,350
Prior years:
Interest accretion	154	152	156
All other incurred	19	(40)	(147)
Total incurred	5,983	5,728	5,359
Paid costs related to:
Current year	3,595	3,488	3,391
Prior years	2,015	1,873	1,808
Total paid	5,610	5,361	5,199
Acquired, net	0	0	23
Foreign currency	42	(11)	(41)
Divestiture of Group Disability and Life business	(5,093)	0	0
Ending balance, net		5,632
Ending balance, net	954		5,276
Add: Reinsurance and other amounts recoverable		184
Add: Reinsurance and other amounts recoverable	159		156
Ending balance		$ 5,816
Ending balance	$ 1,113		$ 5,432