Consolidated Statements of Income - USD ($)	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Revenues	$ 552,644,000	$ 592,225,000	$ 595,740,000
Cost of revenues	429,020,000	466,304,000	470,931,000
Gross profit	123,624,000	125,921,000	124,809,000
General and administrative	64,449,000	65,210,000	63,296,000
Income before income taxes	59,175,000	60,711,000	61,513,000
Income tax provision	12,819,000	13,334,000	14,810,000
Net income	$ 46,356,000	$ 47,377,000	$ 46,703,000
Net income per share:
Basic	$ 2.59	$ 2.59	$ 2.48
Diluted	$ 2.55	$ 2.55	$ 2.46
Weighted average shares outstanding:
Basic	17,930,000	18,326,000	18,794,000
Diluted	18,166,000	18,602,000	19,008,000