Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Common stock, beginning balance (in shares) at Mar. 31, 2019		53,670,000
Equity, beginning balance at Mar. 31, 2019	$ 1,095,831	$ 536	$ 479,150	$ (59,928)	$ (25,747)	$ 701,820
Treasury stock, beginning balance (in shares) at Mar. 31, 2019				1,871,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	$ 1,381		1,381
Exercise of stock options (in shares)	9,300	9,000
Exercise of stock options	$ 275		275
Issuance of shares related to restricted stock (in shares)		62,000
Issuance of shares related to restricted stock	0	$ 1	(1)
Treasury share repurchases (in shares)				977,000
Treasury share repurchases	(29,565)			$ (29,565)
Net income	33,925					33,925
Comprehensive income (loss)	(224)				(224)
Common stock, ending balance (in shares) at Jun. 30, 2019		53,741,000
Equity, ending balance at Jun. 30, 2019	1,101,623	$ 537	480,805	$ (89,493)	(25,971)	735,745
Treasury stock, ending balance (in shares) at Jun. 30, 2019				2,848,000
Common stock, beginning balance (in shares) at Mar. 31, 2020		53,805,000
Equity, beginning balance at Mar. 31, 2020	$ 1,170,971	$ 538	488,116	$ (117,623)	(44,161)	844,101
Treasury stock, beginning balance (in shares) at Mar. 31, 2020	3,719,000			3,719,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	$ 1,464		1,464
Exercise of stock options (in shares)	60,500	60,000
Exercise of stock options	$ 1,216		1,216
Issuance of shares related to restricted stock (in shares)		74,000
Issuance of shares related to restricted stock	0	$ 1	(1)
Treasury share repurchases (in shares)				31,000
Treasury share repurchases	(1,242)			$ (1,242)
Net income	43,706					43,706
Comprehensive income (loss)	10,899				10,899
Common stock, ending balance (in shares) at Jun. 30, 2020		53,939,000
Equity, ending balance at Jun. 30, 2020	$ 1,227,014	$ 539	$ 490,795	$ (118,865)	$ (33,262)	$ 887,807
Treasury stock, ending balance (in shares) at Jun. 30, 2020	3,750,000			3,750,000