Policy Claims and Benefits (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 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	8,382	8,204
Prior Year Claims and Claims Adjustment Expense	162	108
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	8,544	8,312
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(3,394)	(2,937)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(4,683)	(4,775)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(8,077)	(7,712)
Liability for Unpaid Claims and Claims Adjustment Expense, Interest Accretion	27	20
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	(28)	(100)
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments	(1)	(80)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable	6,688	6,672
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	(627)	(508)
Liability for Claims and Claims Adjustment Expense	$ 7,315	$ 7,180