Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 46,703,000	$ 35,695,000	$ 29,479,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	22,984,000	21,775,000	20,948,000
Loss on write down or disposal of assets	306,000	1,199,000	733,000
Stock-based compensation expense	4,349,000	3,164,000	2,432,000
Provision for doubtful accounts	1,875,000	2,559,000	2,335,000
Provision for deferred income taxes	1,456,000	(874,000)	(1,220,000)
Changes in operating assets and liabilities:
Accounts receivable	(8,271,000)	(4,658,000)	(5,429,000)
Customer deposits	(9,772,000)	(3,025,000)	(6,822,000)
Prepaid expenses and income taxes	(66,000)	(2,166,000)	(11,000)
Other assets	145,000	545,000	(29,000)
Accounts and income taxes payable	(1,975,000)	(3,130,000)	3,350,000
Accrued liabilities	20,905,000	11,068,000	6,286,000
Net cash provided by operating activities	78,639,000	62,152,000	52,052,000
CASH FLOWS FROM INVESTING ACTIVITIES
Investment in private equity	0	0	34,000
Purchases of property and equipment	(15,274,000)	(27,689,000)	(31,041,000)
Net cash used in investing activities	(15,274,000)	(27,689,000)	(31,007,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Exercise of employee stock purchase options	503,000	458,000	419,000
Exercise of common stock options	7,241,000	3,426,000	2,367,000
Purchase of treasury stock	(35,167,000)	(11,187,000)	(27,999,000)
Net cash used in financing activities	(27,423,000)	(7,303,000)	(25,213,000)
Net increase (decrease) in cash and cash equivalents	35,942,000	27,160,000	(4,168,000)
Cash and cash equivalents at beginning of year	55,771,000	28,611,000	32,779,000
CASH AND CASH EQUIVALENTS AT END OF YEAR	91,713,000	55,771,000	28,611,000
Supplemental cash flow information
Income taxes paid	12,854,000	16,229,000	18,321,000
Accrual of software license purchase	0	1,746,000	3,492,000
Tenant improvement allowance	$ 0	$ 0	$ 1,224,000