Reinsurance (Details) - Hollenfels - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Incurred and paid claims	$ 4,235	$ 2,907
Claims IBNR	$ 17,293	$ 10,135
Historical Average Claims Ratios, Period, Maximum	10 years