CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income (loss)	$ 11,254	$ (199,567)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	26,925	27,379
Stock-based compensation	72,829	64,358
Expense related to senior note conversions		54,881
Other, net	172	146
Unrealized loss on long term investments	11,962	25,388
Change in fair value of acquisition-related contingent consideration	13,988	14,429
Changes in operating assets and liabilities:
Accounts receivable	(50,011)	(20,758)
Prepaid expenses and other assets	(23,589)	(33,492)
Inventory	1,878	4,462
Accounts payable	7,888	(6,506)
Accrued and other liabilities	(20,055)	12,436
Net cash provided by (used in) operating activities	53,241	(56,844)
Cash flows from investing activities:
Purchase of long term investments	(8,936)	(123,891)
Capital expenditures	(23,381)	(51,466)
Purchases of marketable securities	(58,827)	(115,254)
Sale and maturities of marketable securities	58,694	114,474
Net cash used in investing activities	(32,450)	(176,137)
Cash flows from financing activities:
Proceeds from issuance of common stock under stock plans	18,043	49,461
Cash paid in connection with senior note conversions		(8,934)
Payment of contingent consideration	(9,886)	(8,035)
Net cash provided by financing activities	8,157	32,492
Effect of exchange rates on cash and cash equivalents	135	(43)
Net increase (decrease) in cash, cash equivalents, restricted cash and investments	29,083	(200,532)
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	929,517	452,697
Supplemental Schedule of Cash Flow Information
Interest paid	134	180
Income taxes paid	1,944	5,561
Unpaid purchases of property and equipment		10,866
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	$ 29	351,034
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		$ 330,010