Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net income (loss)	$ (95,751)	$ (74,904)	$ 99,456
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	82,719	77,855	31,216
Stock-based compensation	63,884	44,833	30,192
Gain from sale of discontinued operations			(78,544)
Gain from sale of cost method investment			(1,138)
Loss (gain) on disposal and abandonment of property and equipment	331	(174)
Net unrealized gain on equity investments	(2,441)
Impairment of non-marketable equity investment	7,000
Impairment of intangible assets		47,014
Deferred income taxes	(8,628)	(22,428)	(15,539)
Amortization of deferred tax charge			938
Accretion of convertible debt and amortization of issuance expenses	26,394	24,574	14,178
Amortization of premiums (discount) on marketable securities	(583)	1,040	1,496
Other noncash items	2	(10)	(5)
Changes in assets and liabilities:
Accounts receivable	6,722	(17,392)	(17,028)
Inventories	(1,331)	318	(6,384)
Prepaid expenses and other assets	549	2,272	(1,389)
Income tax payable/receivable	(1,671)	(638)	1,411
Accounts payable	1,963	1,655	3,523
Accrued expenses	(4,902)	(554)	(45)
Deferred revenue	4,997	(3,195)	(1,280)
Other liabilities	(1,095)	(2,958)	2,015
Net cash provided by operating activities	78,159	77,308	63,073
Cash flows from investing activities
Purchases of property and equipment	(31,713)	(37,437)	(22,348)
Proceeds from sale or disposal of property and equipment	145	100
Purchases of marketable securities	(248,038)	(261,247)	(330,592)
Sales of marketable securities	11,654	85,163	5,504
Maturities of marketable securities	242,825	182,299	116,627
Proceeds from sale of equity investment	2,414		6,345
Proceeds from sale of discontinued operations		10,690	78,750
Acquisition of business, net of cash acquired		(1,800)	(294,444)
Payment related to purchase of software license intangible asset	(21,437)	(16,109)	(55)
Purchases of equity investment in private companies	(12,811)		(8,000)
Net cash used in investing activities	(56,961)	(38,341)	(448,213)
Cash flows from financing activities
Proceeds from exercise of stock options	719	2,214	5,748
Proceeds from employee stock purchase plan	5,906	5,776	5,518
Proceeds from issuance of convertible debt, net of issuance costs			279,459
Purchase of capped call options			(22,540)
Minimum tax withholding paid on behalf of employees for net share settlement	(19,118)	(27,673)	(20,477)
Long-term loan	405	333	(725)
Payment of equipment financing obligations	(542)	(1,034)	(20)
Net cash provided by (used in) financing activities	(12,630)	(20,384)	246,963
Net increase (decrease) in cash and cash equivalents	8,568	18,583	(138,177)
Cash and cash equivalents at beginning of year	163,450	144,867	283,044
Cash and cash equivalents at end of year	172,018	163,450	144,867
Supplemental cash flow information
Income taxes paid	2,155	2,158	156
Interest paid	5,818	5,194	2,537
Supplemental disclosure of non-cash investing and financing activities
Software license intangible assets acquired	$ 20,066	$ 2,888	$ 39,046