CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)	$ (135,561)	$ (869)	$ 82,599
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	201,369	21,178	20,977
Amortization of debt issuance costs	4,593	1,450	1,450
Stock-based compensation	41,934	33,959	33,539
Deferred income taxes	(49,932)	7,464	(657)
Provision for excess and obsolete inventories	7,386	3,456	1,960
Restructuring and other related charges (credits)	32,694	2,451	(109)
Cash payments for restructuring charges	(29,463)	(2,942)	(4,001)
Other operating activities	9,640	(305)	2,948
Changes in assets and liabilities, net of acquisition:
Accounts receivable	(10,307)	(12,238)	(13,894)
Inventory	(7,182)	(13,309)	(3,791)
Current and other assets	30,747	(2,480)	1,386
Accounts payable	3,658	2,884	4,377
Accrued liabilities	61,593	(4,164)	13,260
Income taxes	(45,122)	84,613	(657)
Cash provided by operating activities	116,047	121,148	139,387
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of investments	131,300	197,575	157,066
Proceeds from maturities of investments	131,017	211,663	144,092
Purchase of investments	(822)	(373,281)	(300,434)
Acquisition, net of cash acquired	(1,642,241)		0
Capital expenditures	(26,797)	(12,468)	(23,176)
Cash provided from (used for) investing activities	(1,407,543)	23,489	(22,452)
CASH FLOWS FROM FINANCING ACTIVITIES
Repurchase of common stock	(13,177)	(52,948)	(34,236)
Employees' tax withheld and paid for restricted stock and restricted stock units	(14,070)	(11,429)	(9,736)
Proceeds from issuances under stock-based compensation plans	15,730	23,927	15,202
Payment of cash dividends	(22,880)	(19,996)	(19,959)
Proceeds from revolving line of credit	0	8,000	0
Repayments of revolving line of credit	0	(8,000)	0
Repayments of Long-term Debt	(103,188)	0	0
Proceeds from debt issuance, net of issuance costs	1,244,713	0	0
Other financing activity	0	0	761
Cash provided from (used for) financing activities	1,107,128	(60,446)	(47,968)
Effect of exchange rate changes on cash and cash equivalents	(3,784)	4,500	(2,263)
Net increase (decrease) in cash and cash equivalents	(188,152)	88,691	66,704
Cash and cash equivalents at beginning of year	390,661	301,970	235,266
Cash and cash equivalents at end of year	202,509	390,661	301,970
SUPPLEMENTAL DISCLOSURES
Cash paid for income taxes	44,917	9,757	20,948
Cash paid for interest	$ 75,684	$ 27,899	$ 27,783