Policy Claims and Benefits Policy Claims and Benefits (Rollforward of Claims and Claim Adjustment Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense Beginning Balance	$ 6,585	$ 5,896	$ 5,181
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments, Beginning Balance	(433)	(456)	(395)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable, Beginning Balance	6,152	5,440	4,786
Current Year Claims and Claims Adjustment Expense	10,307	10,049	8,912
Prior Year Claims and Claims Adjustment Expense	154	131	14
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	10,461	10,180	8,926
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(5,140)	(4,602)	(4,514)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(5,305)	(4,692)	(4,004)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(10,445)	(9,294)	(8,518)
Interest On Liability For Policy And Contract Claims	33	25	19
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	21	(199)	227
Liability for Unpaid Claims and Claims Adjustment Expense Other	54	(174)	246
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable, Ending Balance	6,222	6,152	5,440
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments, Ending Balance	564	433	456
Liability for Claims and Claims Adjustment Expense, Ending Balance	$ 6,786	$ 6,585	$ 5,896