Policy Claims and Benefits (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense	$ 7,556	$ 6,786
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	(641)	(564)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable	6,915	6,222
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Current Year Claims and Claims Adjustment Expense	7,631	5,740
Prior Year Claims and Claims Adjustment Expense	(122)	(59)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	7,509	5,799
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(2,747)	(1,332)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(4,358)	(3,903)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(7,105)	(5,235)
Liability for Unpaid Claims and Claims Adjustment Expense, Interest Accretion	20	18
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	(38)	(142)
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments	(18)	(124)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable	7,302	6,662
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	(674)	(633)
Liability for Claims and Claims Adjustment Expense	$ 7,976	$ 7,295