CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 40,861	$ 39,124
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	10,265	9,819
Amortization of debt issuance costs	725	483
Stock-based compensation	16,316	16,882
Excess tax benefit from stock-based compensation	(939)	(3,150)
Deferred income taxes	2,499	2,807
Provision for excess and obsolete inventories	1,674	1,084
Restructuring charges/adjustments	(1,463)	0
Cash payments for restructuring charges	(3,736)	0
Other operating activities	(849)	3,037
Changes in assets and liabilities, net of effect of acquisition:
Accounts receivable, net	(8,366)	(2,825)
Inventory, net	(1,102)	(2,166)
Current and other assets	(2,331)	(2,190)
Accounts payable	4,120	9,016
Accrued liabilities	10,444	671
Income taxes	(2,305)	(6,144)
Cash provided by operating activities	65,813	66,448
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of investments	125,504	24,829
Proceeds from maturities of investments	63,853	40,405
Purchase of investments	(192,349)	(61,591)
Capital expenditures	(14,191)	(13,092)
Cash used for investing activities	(17,183)	(9,449)
CASH FLOWS FROM FINANCING ACTIVITIES
Repurchase of common stock	(26,828)	(473,220)
Employees' tax withheld and paid for restricted stock and restricted stock units	(9,123)	(10,499)
Proceeds from issuances under stock-based compensation plans	5,752	9,071
Proceeds from revolving line of credit	0	155,749
Repayments of revolving line of credit	0	(190,249)
Proceeds from bonds issuance, net of issuance costs	0	488,401
Payment of cash dividends	(9,971)	(10,986)
Excess tax benefit from stock-based compensation	939	3,150
Other financing activity	761	0
Cash used for financing activities	(38,470)	(28,583)
Effect of exchange rate changes on cash and cash equivalents	(971)	(430)
Net increase in cash and cash equivalents	9,189	27,986
Cash and cash equivalents at beginning of period	235,266	276,850
Cash and cash equivalents at end of period	$ 244,455	$ 304,836