Consolidated Statements of Comprehensive Earnings - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net earnings	$ 113,056	$ 110,993	$ 57,284
Other comprehensive earnings (loss)
Unrealized gain (loss) on marketable securities, net of tax	10,575	(2,411)	(613)
Other comprehensive earnings (loss)	10,575	(2,411)	(613)
Comprehensive earnings	$ 123,631	$ 108,582	$ 56,671