Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net income	$ 40,609	$ 32,428	$ 37,265
Adjustments to reconcile net income to cash provided by operating activities, net of the effects of acquisitions:
Depreciation and amortization	17,464	16,642	13,877
Loss on extinguishment of debt	0	553	0
Loss on disposal of fixed assets	104	168	127
Deal related compensation expense and accretion charges	263	106	0
Share-based compensation expense associated with equity awards	9,591	8,651	6,439
Net change in fair value of contingent and contractual liabilities	466	0	0
Deferred income taxes	3,909	5,437	3,459
Other gains	(3)	(53)	0
Changes in assets and liabilities
Accounts receivable	82	(3,997)	2,755
Inventories	1,433	(892)	(1,092)
Prepaid expenses and other assets	5,391	(875)	404
Accounts payable	(2,345)	(2,195)	2,583
Accrued compensation and other expenses	10,739	1,637	3,438
Contingent liabilities	0	389	0
Income taxes payable	114	0	0
Deferred revenue	7,595	10,308	(2,066)
Net cash provided by operating activities	95,412	68,307	67,189
Cash flows from investing activities:
Purchase of marketable securities	(121,133)	(117,682)	(153,903)
Proceeds from maturity of marketable securities	163,416	184,899	101,430
Purchase of fixed assets	(11,948)	(11,288)	(7,491)
Acquisition of businesses, net of cash acquired	(51,273)	(46,721)	0
Increase in deposits	(804)	0	0
Net cash (used in) provided by investing activities	(21,742)	9,208	(59,964)
Cash flows from financing activities:
Issuance of common stock under stock plans	575	473	(367)
Payment of contingent consideration	(4,038)	(846)	0
Treasury stock repurchases	(27,448)	(20,595)	0
Proceeds from issuance of long-term debt, net of issuance costs	0	60,691	0
Repayment of long-term debt	(62,000)	(68,106)	(11,250)
Excess tax benefit from share-based compensation awards	1,907	965	8,238
Net cash used in financing activities	(91,004)	(27,418)	(3,379)
Effect of exchange rate changes on cash and cash equivalents	9	(10)	0
Net (decrease) increase in cash and cash equivalents	(17,325)	50,087	3,846
Cash and cash equivalents, beginning of year	117,255	67,168	63,322
Cash and cash equivalents, end of year	99,930	117,255	67,168
Supplemental disclosures of cash flow information:
Cash paid for interest	325	1,253	2,079
Cash paid for income taxes	13,326	13,163	7,846
Non-cash transactions:
Transfers of inventory to fixed assets	583	1,910	1,348
Additions to property, plant and equipment included in accounts payable	154	569	979
Fair value of contingent consideration related to acquisitions, included in contingent liabilities	0	8,000	0
Gross decrease in contractual liability relating to fair value adjustment	(184)	(900)	0
Gross increase in contingent consideration liability relating to fair value adjustment	650	900	0
Issuance of common stock under employee stock plans	4,545	0	0
Debt Issuance Costs Settled
Non-cash transactions:
Issuance of additional debt	0	1,184	0
Interest Settled
Non-cash transactions:
Issuance of additional debt	$ 0	$ 125	$ 0