Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Cash flows from operating activities:
Net income	$ 32,428	$ 37,265	$ 27,917
Adjustments to reconcile net income to cash provided by operating activities, net of the effects of acquisitions:
Depreciation and amortization	16,642	13,877	14,357
Loss on extinguishment of debt	553	0	0
Loss on disposal of fixed assets	168	127	258
Acquisition related compensation expense and accretion charges	106	0	0
Share-based compensation expense associated with equity awards	8,651	6,439	5,456
Deferred income taxes	5,437	3,459	5,189
Other gains	(53)	0	0
Changes in assets and liabilities
Accounts receivable	(3,997)	2,755	(25,729)
Inventories	(892)	(1,092)	(3,432)
Prepaid expenses and other assets	(875)	404	5,254
Accounts payable	(2,195)	2,583	(238)
Accrued compensation and other expenses	1,637	3,438	(3,966)
Contingent liabilities	389	0	0
Income taxes payable	0	0	(1,702)
Deferred revenue	10,308	(2,066)	22,290
Net cash provided by operating activities	68,307	67,189	45,654
Cash flows from investing activities:
Purchase of marketable securities	(117,682)	(153,903)	(92,919)
Proceeds from maturity of marketable securities	184,899	101,430	39,064
Purchase of fixed assets	(11,288)	(7,491)	(5,242)
Capitalized software development costs	0	0	(408)
Acquisition of businesses, net of cash acquired	(46,721)	0	0
Net cash provided by (used in) investing activities	9,208	(59,964)	(59,505)
Cash flows from financing activities:
Issuance of common stock under stock plans	473	(367)	3,039
Payment of contingent consideration	(846)	0	0
Treasury stock repurchases	(20,595)	0	0
Proceeds from issuance of long-term debt, net of issuance costs	60,691	0	0
Repayment of long-term debt	(68,106)	(11,250)	(13,144)
Excess tax benefit from share-based compensation awards	965	8,238	5,056
Net cash used in financing activities	(27,418)	(3,379)	(5,049)
Effect of exchange rate changes on cash and cash equivalents	(10)	0	0
Net increase (decrease) in cash and cash equivalents	50,087	3,846	(18,900)
Cash and cash equivalents, beginning of year	67,168	63,322	82,222
Cash and cash equivalents, end of year	117,255	67,168	63,322
Supplemental disclosures of cash flow information:
Cash paid for interest	1,253	2,079	3,063
Cash paid for income taxes	13,163	7,846	2,897
Non-cash transactions:
Transfers of inventory to fixed assets	1,910	1,348	1,570
Additions to property, plant and equipment included in accounts payable	569	979	1,160
Fair value of contingent liability	8,213	0	0
Debt Issuance Costs Settled [Member]
Non-cash transactions:
Issuance of additional debt	1,184	0	0
Interest Settled [Member]
Non-cash transactions:
Issuance of additional debt	125	0	0
Decrease In Contractual Non-Compliance Liability [Member]
Non-cash transactions:
(Decrease) Increase in liability relating to fair value adjustment	(900)	0	0
Increase In Contingent Liability [Member]
Non-cash transactions:
(Decrease) Increase in liability relating to fair value adjustment	$ 900	$ 0	$ 0