Segment and Other Operating Information - Net Earnings (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Net earnings	$ 39,840	$ 10,825	$ 151,869	$ 57,176
Segments
Segment Reporting Information [Line Items]
Net earnings	35,881	6,046	144,094	47,175
Segment Reconciling Items
Segment Reporting Information [Line Items]
Realized gains on investments, net of taxes	$ 3,959	$ 4,779	$ 7,775	$ 10,001