CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 55,412	$ 86,477
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,838	13,975
Amortization of debt issuance costs	845	0
Stock-based compensation	24,599	21,122
Excess tax benefit from stock-based compensation	(3,300)	(2,988)
Deferred income taxes	2,185	1,654
Provision for excess and obsolete inventories	1,319	992
Non-cash restructuring charges	8,433	0
Other operating activities	5,896	484
Changes in assets and liabilities, net of effect of acquisition:
Accounts receivable, net	1,279	(18,479)
Inventory, net	(352)	(920)
Current and other assets	(264)	(4,680)
Accounts payable	5,744	2,395
Accrued liabilities	(3,841)	3,464
Income taxes	(8,770)	(3,120)
Cash provided by operating activities	104,023	100,376
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of investments	56,890	72,564
Proceeds from maturities of investments	51,895	102,175
Purchase of investments	(206,110)	(172,757)
Acquisition, net of cash acquired	0	(150)
Capital expenditures	(20,977)	(19,214)
Cash used for investing activities	(118,302)	(17,382)
CASH FLOWS FROM FINANCING ACTIVITIES
Repurchase of common stock	(482,776)	(27,443)
Employees' tax withheld and paid for restricted stock and restricted stock units	(10,804)	(7,306)
Proceeds from issuances under stock-based compensation plans	9,854	17,821
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	488,401	0
Payment of cash dividends	(16,034)	(19,296)
Excess tax benefit from stock-based compensation	3,300	2,988
Cash used for financing activities	(42,559)	(33,236)
Effect of exchange rate changes on cash and cash equivalents	(921)	(2,112)
Net increase (decrease) in cash and cash equivalents	(57,759)	47,646
Cash and cash equivalents at beginning of period	276,850	232,704
Cash and cash equivalents at end of period	$ 219,091	$ 280,350