Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating activities:
Net income	$ 171,211	$ 185,056
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,427	9,936
Bad debt expense	241	578
Stock-based compensation	37,019	43,757
Write-down of inventory and other	3,984	3,152
Accretion on marketable securities	(2,678)	(1,644)
Change in fair value of other investments	(17,407)
Deferred tax provision	30,551	(25,992)
Change in fair value of contingent consideration	865	93
Other non-cash operating activities	3,167
Changes in assets and liabilities:
Accounts receivable	(10,333)	(19,268)
Inventories	(13,261)	(26,522)
Prepaid expenses and other assets	(4,250)	678
Accounts payable	841	4,909
Accrued expenses and other liabilities	11,193	6,909
Deferred revenue	2,757	164
Net cash provided by operating activities	228,327	181,806
Investing activities:
Purchases of marketable securities	(491,513)	(241,745)
Proceeds from the sale and maturity of marketable securities and other	410,456	226,949
Purchases of other investments and intangible assets	(20,899)	(30,436)
Purchases of property and equipment	(33,460)	(35,469)
Net cash used for investing activities	(135,416)	(80,701)
Financing activities:
Proceeds from the exercise of stock options	3,165	11,043
Taxes paid related to net share settlement upon vesting of stock awards	(41,607)	(71,213)
Repurchase of common stock	(59,876)
Proceeds from the issuance of stock under employee stock purchase plan	2,368	1,376
Net cash used for financing activities	(95,950)	(58,794)
Effect of exchange rate changes on cash	(12)	(1,105)
Net (decrease) increase in cash and cash equivalents	(3,051)	41,206
Cash and cash equivalents at beginning of period	121,021	42,975
Cash and cash equivalents at end of period	117,970	84,181
Supplemental disclosure of cash flow information:
Cash paid for income taxes	7,479	4,500
Supplemental disclosure of non-cash activities:
Property and equipment in accounts payable and accrued expenses	3,314	$ 1,670
Right-of-use assets obtained in exchange for lease liabilities	$ 14,596