Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Net loss	$ (22,745)	$ (22,991)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	24,193	18,886
Stock-based compensation	18,758	14,553
Deferred income taxes	970	(9,156)
Accretion of convertible debt and amortization of debt issuance costs	6,799	6,330
Net unrealized gain on equity investments	(272)	(3,023)
Amortization of premiums on marketable securities	(258)	(36)
Other non-cash items	290	10
Changes in assets and liabilities:
Accounts receivable	3,216	19,137
Inventories	1,313	(3,016)
Prepaid expenses and other assets	(969)	(84)
Income tax payable/receivable	281	(728)
Accounts payable	(2,065)	776
Accrued expenses	(3,025)	(3,920)
Deferred revenue	427	(43)
Other liabilities	(998)	499
Net cash provided by operating activities	25,915	17,194
Cash flows from investing activities
Purchases of property and equipment	(4,389)	(14,527)
Proceeds from insurance claim		125
Purchases of marketable securities	(48,054)	(86,177)
Sales of marketable securities	6,464	1,857
Maturities of marketable securities	73,071	76,815
Payments related to purchase of intangible assets	(7,180)	(6,271)
Proceeds from sale of equity investment		2,414
Purchase of equity investments		(12,811)
Net cash provided by (used in) investing activities	19,912	(38,575)
Cash flows from financing activities
Proceeds from exercise of stock options	646	291
Proceeds from employee stock purchase plan purchases	3,477	3,704
Payment of obligations related to equipment financing	(125)	(175)
Repayment of long-term loan		123
Minimum tax withholding paid on behalf of employees for net share settlement	(3,995)	(1,912)
Net cash provided by financing activities	3	2,031
Net increase (decrease) in cash and cash equivalents	45,830	(19,350)
Cash and cash equivalents at beginning of period	172,018	163,450
Cash and cash equivalents at end of period	217,848	144,100
Supplemental cash flow information:
Interest paid	1,529	1,295
Income taxes paid	57	1,626
Supplemental disclosure of non-cash investing and financing activities:
Purchase of marketable securities not paid	6,514	1,248
Software license intangible assets acquired	$ 1,880	$ 2,923