Policy Claims and Benefits Policy Claims and Benefits (Rollforward of Claims and Claim Adjustment Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense Beginning Balance	$ 6,786	$ 6,585	$ 5,896
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments, Beginning Balance	(564)	(433)	(456)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable, Beginning Balance	6,222	6,152	5,440
Current Year Claims and Claims Adjustment Expense	11,195	10,307	10,049
Prior Year Claims and Claims Adjustment Expense	123	154	131
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	11,318	10,461	10,180
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(5,617)	(5,140)	(4,602)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(5,204)	(5,305)	(4,692)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(10,821)	(10,445)	(9,294)
Interest On Liability For Policy And Contract Claims	36	33	25
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	160	21	(199)
Liability for Unpaid Claims and Claims Adjustment Expense Other	196	54	(174)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable, Ending Balance	6,915	6,222	6,152
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments, Ending Balance	641	564	433
Liability for Claims and Claims Adjustment Expense, Ending Balance	$ 7,556	$ 6,786	$ 6,585