Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Incurred and paid claims	$ 24,380	$ 14,800
Historical Average Claims Ratios, Period, Maximum	10 years
Hollenfels
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Claims IBNR	$ 5,647	$ 11,800