CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Operating activities:
Net income	$ 14,814	$ 3,729
Adjustments required to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,796	1,863
Bad debt expense	43	11
Stock-based compensation	12,696	8,367
Write-down of inventory	1,135	641
Deferred tax provision	675	679
Change in fair value of contingent consideration	365
Unrealized losses on investments	18
Changes in assets and liabilities:
Accounts receivable	(4,320)	123
Inventories	(3,582)	(69)
Prepaid expenses and other assets	(198)	(345)
Accounts payable	368	(1,679)
Accrued expenses and other long-term liabilities	(639)	104
Deferred revenue	1,856	147
Net cash provided by operating activities	25,027	13,571
Investing activities:
Purchases of marketable securities	(72,411)	(58,330)
Proceeds from the sale and maturity of marketable securities	57,890	52,264
Acquisition of ECP and AIS, net of cash assumed	(15,697)
Purchase of other investment	(1,250)	(750)
Purchases of property and equipment	(2,232)	(2,301)
Net cash used for investing activities	(33,700)	(9,117)
Financing activities:
Proceeds from the exercise of stock options	8,624	8,227
Payments in lieu of issuance of common stock for minimum payroll taxes	(1,013)	(426)
Proceeds from the issuance of stock under employee stock purchase plan	397	312
Net cash provided by financing activities	8,008	8,113
Effect of exchange rate changes on cash	(773)	614
Net (decrease) increase in cash and cash equivalents	(1,438)	13,181
Cash and cash equivalents at beginning of period	20,916	9,451
Cash and cash equivalents at end of period	19,478	22,632
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1,090	1,106
Supplemental disclosure of non-cash investing and financing activities:
Contingent consideration related to acquisition of ECP	6,000
Fixed asset expenditures incurred, not yet paid	$ 501	$ 92