CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 38,781	$ 40,861
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	10,743	10,265
Amortization of debt issuance costs	725	725
Stock-based compensation	18,018	16,316
Deferred income taxes	4,384	2,499
Provision for excess and obsolete inventories	900	1,674
Restructuring and related charges (credits)	2,522	(1,463)
Cash payments for restructuring charges	(2,429)	(3,736)
Other operating activities	(1,141)	(849)
Changes in assets and liabilities:
Accounts receivable, net	1,246	(8,366)
Inventory, net	(5,844)	(1,102)
Current and other assets	(4,539)	(2,331)
Accounts payable	3,205	4,120
Accrued liabilities	(9,388)	10,444
Income taxes	(7,890)	(2,305)
Cash provided by operating activities	49,293	66,752
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of investments	30,895	125,504
Proceeds from maturities of investments	106,661	63,853
Purchase of investments	(133,949)	(192,349)
Capital expenditures	(6,752)	(14,191)
Cash used for investing activities	(3,145)	(17,183)
CASH FLOWS FROM FINANCING ACTIVITIES
Repurchase of common stock	(39,222)	(26,828)
Employees' tax withheld and paid for restricted stock and restricted stock units	(10,789)	(9,123)
Proceeds from issuances under stock-based compensation plans	11,950	5,752
Payment of cash dividends	(10,057)	(9,971)
Other financing activity	0	761
Cash used for financing activities	(48,118)	(39,409)
Effect of exchange rate changes on cash and cash equivalents	3,116	(971)
Net increase in cash and cash equivalents	1,146	9,189
Cash and cash equivalents at beginning of period	301,970	235,266
Cash and cash equivalents at end of period	303,116	244,455
SUPPLEMENTAL NON-CASH DISCLOSURES
Accounts payable for purchases of property, plant and equipment	$ 3,407	$ 2,718