Consolidated Statements of Income - USD ($)	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 592,225,000	$ 595,740,000	$ 558,350,000
Cost of revenues	466,304,000	470,931,000	451,097,000
Gross profit	125,921,000	124,809,000	107,253,000
General and administrative	65,210,000	63,296,000	59,350,000
Income before income taxes	60,711,000	61,513,000	47,903,000
Income tax provision	13,334,000	14,810,000	12,208,000
Net income	$ 47,377,000	$ 46,703,000	$ 35,695,000
Net income per share:
Basic	$ 2.59	$ 2.48	$ 1.90
Diluted	$ 2.55	$ 2.46	$ 1.87
Weighted average shares outstanding:
Basic	18,326,000	18,794,000	18,825,000
Diluted	18,602,000	19,008,000	19,042,000