Policy Claims and Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense	$ 6,904	$ 6,934	$ 6,786	$ 6,585
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	(580)	(500)	(564)	(433)
Liability For Unpaid Claims And Claims Adjustment Expense Net Of Recoverable	6,324	6,434	$ 6,222	$ 6,152
Current Year Claims and Claims Adjustment Expense	2,838	2,808
Prior Year Claims and Claims Adjustment Expense	11	31
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	2,849	2,839
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(131)	(187)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(2,342)	(2,387)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(2,473)	(2,574)
Interest On Liability For Policy And Contract Claims	9	7
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	(283)	10
Liability for Unpaid Claims and Claims Adjustment Expense Other	$ (274)	$ 17