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	$ 3,902		3,902
Exercise of stock options (in shares)	18,400	18,000
Exercise of stock options	$ 544		544
Issuance of shares related to restricted stock (in shares)		67,000
Issuance of shares related to restricted stock	0	$ 1	(1)
Treasury share repurchases (in shares)				1,652,000
Treasury share repurchases	(50,856)			$ (50,856)
Net income	67,177					67,177
Comprehensive income (loss)	(3,808)				(3,808)
Common stock, ending balance (in shares) at Sep. 30, 2019		53,755,000
Equity, ending balance at Sep. 30, 2019	1,112,790	$ 537	483,595	$ (110,784)	(29,555)	768,997
Treasury stock, ending balance (in shares) at Sep. 30, 2019				3,523,000
Common stock, beginning balance (in shares) at Jun. 30, 2019		53,741,000
Equity, beginning balance at Jun. 30, 2019	1,101,623	$ 537	480,805	$ (89,493)	(25,971)	735,745
Treasury stock, beginning balance (in shares) at Jun. 30, 2019				2,848,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	2,521		2,521
Exercise of stock options (in shares)		9,000
Exercise of stock options	269		269
Issuance of shares related to restricted stock (in shares)		5,000
Issuance of shares related to restricted stock	0
Treasury share repurchases (in shares)				675,000
Treasury share repurchases	(21,291)			$ (21,291)
Net income	33,252					33,252
Comprehensive income (loss)	(3,584)				(3,584)
Common stock, ending balance (in shares) at Sep. 30, 2019		53,755,000
Equity, ending balance at Sep. 30, 2019	1,112,790	$ 537	483,595	$ (110,784)	(29,555)	768,997
Treasury stock, ending balance (in shares) at Sep. 30, 2019				3,523,000
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	$ 4,356		4,356
Exercise of stock options (in shares)	62,800	62,000
Exercise of stock options	$ 1,285		1,285
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)				60,000
Treasury share repurchases	(2,239)			$ (2,239)
Net income	88,295					88,295
Comprehensive income (loss)	15,549				15,549
Common stock, ending balance (in shares) at Sep. 30, 2020		53,941,000
Equity, ending balance at Sep. 30, 2020	$ 1,278,217	$ 539	493,756	$ (119,862)	(28,612)	932,396
Treasury stock, ending balance (in shares) at Sep. 30, 2020	3,779,000			3,779,000
Common stock, beginning balance (in shares) at Jun. 30, 2020		53,939,000
Equity, beginning balance at Jun. 30, 2020	$ 1,227,014	$ 539	490,795	$ (118,865)	(33,262)	887,807
Treasury stock, beginning balance (in shares) at Jun. 30, 2020				3,750,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	2,892		2,892
Exercise of stock options (in shares)		2,000
Exercise of stock options	69		69
Treasury share repurchases (in shares)				29,000
Treasury share repurchases	(997)			$ (997)
Net income	44,589					44,589
Comprehensive income (loss)	4,650				4,650
Common stock, ending balance (in shares) at Sep. 30, 2020		53,941,000
Equity, ending balance at Sep. 30, 2020	$ 1,278,217	$ 539	$ 493,756	$ (119,862)	$ (28,612)	$ 932,396
Treasury stock, ending balance (in shares) at Sep. 30, 2020	3,779,000			3,779,000