CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 21,228	$ 28,672
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,986	4,624
Amortization of debt issuance costs	121	0
Stock-based compensation	8,050	6,305
Excess tax benefit from stock-based compensation	(2,391)	(992)
Deferred income taxes	4,146	2,715
Provision for excess and obsolete inventories	402	379
Other operating activities	4,537	581
Changes in assets and liabilities, net of effect of acquisition:
Accounts receivable, net	8,579	(12,631)
Inventory, net	358	(3,983)
Current and other assets	(2,869)	(970)
Accounts payable	4,958	5,995
Accrued liabilities	(6,212)	(4,520)
Income taxes	(2,419)	3,363
Cash provided by operating activities	43,474	29,538
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of investments	16,375	5,014
Proceeds from maturities of investments	25,425	50,900
Purchase of investments	(43,834)	(54,867)
Capital expenditures	(3,966)	(7,312)
Cash used for investing activities	(6,000)	(6,265)
CASH FLOWS FROM FINANCING ACTIVITIES
Repurchase of common stock	(284,444)	(12,438)
Employees' tax withheld and paid for restricted stock and restricted stock units	(9,903)	(5,787)
Proceeds from issuances under stock-based compensation plans	3,077	2,832
Proceeds from revolving line of credit	155,749	0
Repayments of revolving line of credit	(190,249)	0
Proceeds from bonds issuance, net of issuance costs	489,670	0
Payment of cash dividends	(5,828)	(6,389)
Excess tax benefit from stock-based compensation	2,391	992
Cash provided by (used for) financing activities	160,463	(20,790)
Effect of exchange rate changes on cash and cash equivalents	592	63
Net increase in cash and cash equivalents	198,529	2,546
Cash and cash equivalents at beginning of period	276,850	232,704
Cash and cash equivalents at end of period	$ 475,379	$ 235,250