CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 18,828	$ 20,387
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,382	5,146
Amortization of debt issuance costs	362	362
Stock-based compensation	9,256	8,413
Deferred income taxes	6,606	4,890
Provision for excess and obsolete inventories	529	772
Restructuring and related charges (credits)	2,573	(1,048)
Cash payments for restructuring charges	(1,905)	(2,788)
Other operating activities	503	(1,920)
Changes in assets and liabilities:
Accounts receivable, net	6,465	(4,529)
Inventory, net	(2,241)	(1,486)
Current and other assets	(2,704)	(672)
Accounts payable	989	7,055
Accrued liabilities	(18,467)	(1,370)
Income taxes	(13,291)	(2,736)
Cash provided by operating activities	12,885	30,476
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of investments	21,571	74,349
Proceeds from maturities of investments	58,298	34,353
Purchase of investments	(83,279)	(106,711)
Capital expenditures	(3,047)	(7,579)
Cash used for investing activities	(6,457)	(5,588)
CASH FLOWS FROM FINANCING ACTIVITIES
Repurchase of common stock	(13,492)	(18,639)
Employees' tax withheld and paid for restricted stock and restricted stock units	(10,485)	(8,792)
Proceeds from issuances under stock-based compensation plans	9,204	733
Payment of cash dividends	(5,014)	(4,970)
Cash used for financing activities	(19,787)	(31,668)
Effect of exchange rate changes on cash and cash equivalents	1,873	(1,013)
Net decrease in cash and cash equivalents	(11,486)	(7,793)
Cash and cash equivalents at beginning of period	301,970	235,266
Cash and cash equivalents at end of period	290,484	227,473
SUPPLEMENTAL NON-CASH DISCLOSURES
Accounts payable for purchases of property, plant and equipment	$ 3,823	$ 3,577