Computation of Net Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Computation of Net Earnings per Share
Net income available to common stockholders	$ 556	$ 6,062	$ 14,669	$ 13,915	$ 6,618	$ 28,584
Weighted average common shares outstanding used in computing basic income per share	32,729		32,214		32,706	32,154
Incremental options and RSUs	1,172		1,728		1,358	1,894
Weighted average common shares used in computing diluted net income per share	33,901		33,942		34,064	34,048
Net income per share
Basic	$ 0.02		$ 0.46		$ 0.20	$ 0.89
Diluted	$ 0.02		$ 0.43		$ 0.19	$ 0.84
Weighted average number diluted shares outstanding adjustment	200		300		10	10