CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income (loss)	$ 40,430	$ (163,513)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	40,743	39,319
In-process research and development impairment		12,000
Stock-based compensation	110,830	99,287
Expense related to senior note conversions		54,881
Other, net	258	216
Unrealized loss on long term investments	21,911	2,343
Change in fair value of acquisition-related contingent consideration	18,708	(1,914)
Changes in operating assets and liabilities:
Accounts receivable	18,563	(49,587)
Prepaid expenses and other assets	(21,330)	(32,051)
Inventory	3,030	4,741
Accounts payable	27,807	(5,666)
Accrued and other liabilities	(8,561)	36,223
Net cash provided by (used in) operating activities	252,389	(3,721)
Cash flows from investing activities:
Purchase of long term investments	(8,936)	(123,891)
Capital expenditures	(48,202)	(85,770)
Purchases of marketable securities	(104,228)	(131,919)
Sale and maturities of marketable securities	111,040	134,604
Net cash used in investing activities	(50,326)	(206,976)
Cash flows from financing activities:
Proceeds from issuance of common stock under stock plans	20,480	58,554
Proceeds from issuance of common stock, net		649,387
Cash paid in connection with senior note conversions		(8,934)
Payment of contingent consideration	(9,886)	(12,521)
Net cash provided by financing activities	10,594	686,486
Effect of exchange rates on cash and cash equivalents	97	(46)
Net increase in cash, cash equivalents, restricted cash and investments	212,754	475,743
Cash, cash equivalents, restricted cash and investments at beginning of period	900,434	653,229
Cash, cash equivalents, restricted cash and investments at end of period	1,113,188	1,128,972
Supplemental Schedule of Cash Flow Information
Interest paid	134	180
Income taxes paid	2,932	6,187
Unpaid purchases of property and equipment		10,774
Convertible Senior Notes 0.375 Percent Due 2018
Supplemental Schedule of Cash Flow Information
Reclassification to common stock and additional paid in capital in connection with conversions or exchange of convertible senior notes	$ 31	351,041
Convertible Senior Notes 1.25 Percent Due 2020
Supplemental Schedule of Cash Flow Information
Reclassification to common stock and additional paid in capital in connection with conversions or exchange of convertible senior notes		$ 330,011