Reserves for Losses and Loss Settlement Expenses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross liability for losses and loss settlement expenses at beginning of year	$ 1,421,754	$ 1,312,483
Ceded losses and loss settlement expenses at beginning of year	(68,536)	(57,094)
Net liability for losses and loss settlement expenses at beginning of year	1,353,218	1,255,389
Losses and loss settlement expenses incurred for claims occurring during
Current year	200,250	835,507
Prior years	(13,747)	(5,335)
Total incurred	186,503	830,172
Losses and loss settlement expense payments for claims occurring during
Current year	50,191	333,975
Prior years	144,860	398,368
Total paid	195,051	732,343
Net liability for losses and loss settlement expenses at end of year	1,344,670	1,353,218
Ceded losses and loss settlement expenses at end of year	93,735	68,536
Gross liability for losses and loss settlement expenses at end of period	$ 1,438,405	$ 1,421,754