Policy Claims and Benefits (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense	$ 6,786	$ 6,585
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	(564)	(433)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable	6,222	6,152
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Current Year Claims and Claims Adjustment Expense	5,740	5,457
Prior Year Claims and Claims Adjustment Expense	59	58
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	5,799	5,515
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(1,332)	(1,063)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(3,903)	(3,979)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(5,235)	(5,042)
Liability for Unpaid Claims and Claims Adjustment Expense, Interest Accretion	18	13
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	(142)	3
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments	(124)	16
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable	6,662	6,641
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	633	525
Liability for Claims and Claims Adjustment Expense	$ 7,295	$ 7,166