Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Operating activities:
Net income (loss)	$ 15,014	$ 1,495	$ (11,755)
Adjustments required to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	2,723	4,336	3,948
Bad debt expense	33	117	139
Stock-based compensation	9,501	7,773	5,421
Write-down of inventory	1,172	1,833	2,781
Loss on disposal of fixed assets	10	53	29
Deferred tax provision	755	789	970
Gain on sale of WorldHeart common stock			(456)
Gain on settlement of investment		(1,017)
Changes in assets and liabilities:
Accounts receivable	(2,586)	(5,284)	(1,923)
Inventories	(5,315)	(6,229)	(1,508)
Prepaid expenses and other assets	(326)	(239)	161
Accounts payable	1,183	287	2,480
Accrued expenses and other long-term liabilities	3,057	(1,330)	605
Deferred revenue	1,178	1,050	682
Net cash provided by operating activities	26,399	3,634	1,574
Investing activities:
Purchases of marketable securities	(49,429)	(24,502)	(8,004)
Proceeds from the sale and maturity of marketable securities	42,000	7,750	7,000
Proceeds from the sale of WorldHeart common stock			456
Proceeds from settlement of investment		1,017
Purchases of property and equipment	(2,836)	(1,745)	(1,804)
Net cash used for investing activities	(10,265)	(17,480)	(2,352)
Financing activities:
Proceeds from the exercise of stock options	2,936	14,257	1,061
Repurchase of common stock	(15,045)
Payments in lieu of issuance of common stock for minimum payroll taxes	(257)
Proceeds from the issuance of stock under employee stock purchase plan	555	423	313
Net cash (used for) provided by financing activities	(11,811)	14,680	1,374
Effect of exchange rate changes on cash	(862)	(675)	447
Net increase in cash and cash equivalents	3,461	159	1,043
Cash and cash equivalents at beginning of year	5,990	5,831	4,788
Cash and cash equivalents at end of year	9,451	5,990	5,831
Supplemental disclosures:
Fixed asset expenditures incurred, not yet paid	$ 250	$ 535	$ 48