CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands	6 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 54,252	$ 51,375
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,849	7,765
Stock-based compensation	8,688	7,789
Provisions for sales allowances and doubtful accounts	100	238
Provision for excess and obsolete inventories	1,321	242
Benefit from deferred income taxes	(5,765)	(2,846)
Income tax benefit associated with stock option exercises	1,924	1,457
Excess tax benefit from stock-based compensation	(3,360)	(907)
Amortization of premium on investments, net	849	0
Other operating activities	289	189
Changes in assets and liabilities:
Accounts receivable, net	246	(6,802)
Inventory, net	(5,390)	334
Current and other assets	(408)	(1,212)
Accounts payable	(8,883)	(4,064)
Accrued liabilities	(6,762)	(945)
Income taxes	12,630	4,672
Cash provided by operating activities	56,580	57,285
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of short-term investments	66,060	23,250
Proceeds from maturities of short-term investments	83,108	0
Purchase of short-term investments	(88,783)	(64,842)
Proceeds from sales of long-term investments	4,936	0
Purchase of long-term investments	(45,194)	(14,739)
Capital expenditures and other assets	(10,044)	(6,227)
Cash provided by (used for) investing activities	10,083	(62,558)
CASH FLOWS FROM FINANCING ACTIVITIES
Repurchase of common stock	(184,067)	(59,979)
Equity forward contract related to accelerated share repurchase program	(15,000)	0
Proceeds from sale of treasury stock	2,519	2,022
Proceeds from issuance of common stock	16,664	11,079
Proceeds from revolving line of credit	17,500	0
Payment of cash dividends	(4,720)	(4,838)
Employees taxes withheld and paid for restricted stock and restricted stock units	(880)	(62)
Excess tax benefit from stock-based compensation	3,360	907
Cash used for financing activities	(164,624)	(50,871)
Effect of exchange rate changes on cash and cash equivalents	(1,037)	612
Net decrease in cash and cash equivalents	(98,998)	(55,532)
Cash and cash equivalents at beginning of period	284,375	349,961
Cash and cash equivalents at end of period	$ 185,377	$ 294,429