Earnings Per Share (Computation of basic and diluted earnings per share) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Numerator for basic and diluted earnings per share:
Net income (loss)	$ 15,250	$ 16,599	$ 18,579	$ (782)	$ 15,912	$ 7,706	$ 50,428	$ 22,836
Denominators:
Average basic shares outstanding	23,679,000			23,348,000			23,581,000	23,245,000
Effect of dilutive employee stock options and other share-based awards	352,000			0			344,000	402,000
Average diluted shares outstanding	24,031,000			23,348,000			23,925,000	23,647,000