Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Net income	$ 101,994	$ 140,193
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	9,052	6,347
Bad debt expense	152	467
Stock-based compensation	26,445	28,179
Write-down of inventory and other	2,157	1,733
Accretion on marketable securities	(2,276)	(848)
Change in fair value of other investments	5,943
Deferred tax provision	10,195	(45,676)
Change in fair value of contingent consideration	661	3
Other non-cash operating activities	2,177
Changes in assets and liabilities:
Accounts receivable	(3,828)	(5,131)
Inventories	(12,204)	(16,750)
Prepaid expenses and other assets	(4,077)	(1,987)
Accounts payable	781	761
Accrued expenses and other liabilities	(1,268)	826
Deferred revenue	2,983	(926)
Net cash provided by operating activities	138,887	107,191
Investing activities:
Purchases of marketable securities	(268,485)	(112,956)
Proceeds from the sale and maturity of marketable securities and other	262,881	136,844
Purchases of other investments and intangible assets	(7,800)	(11,426)
Purchases of property and equipment	(24,607)	(27,345)
Net cash used for investing activities	(38,011)	(14,883)
Financing activities:
Proceeds from the exercise of stock options	2,706	10,613
Taxes paid related to net share settlement upon vesting of stock awards	(41,206)	(69,666)
Repurchase of common stock	(34,873)
Proceeds from the issuance of stock under employee stock purchase plan	2,368	1,375
Net cash used for financing activities	(71,005)	(57,678)
Effect of exchange rate changes on cash	(613)	(1,223)
Net increase in cash and cash equivalents	29,258	33,407
Cash and cash equivalents at beginning of period	121,021	42,975
Cash and cash equivalents at end of period	150,279	76,382
Supplemental disclosure of cash flow information:
Cash paid for income taxes	6,349	3,530
Supplemental disclosure of non-cash activities:
Property and equipment in accounts payable and accrued expenses	3,825	$ 1,399
Right-of-use assets obtained in exchange for lease liabilities	$ 14,513