Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income (loss)	$ 280,717	$ (72,253)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Stock-based compensation expense	141,564	117,414
Depreciation and amortization expense	29,740	31,378
Write-downs of inventories to net realizable value	9,479	0
Deferred income taxes	4,626	22,858
Impairment of property and equipment	1,946	0
Other non-cash items, net	(4,834)	3,436
Changes in operating assets and liabilities:
Accounts receivable, net	(41,450)	(12,954)
Inventories	(22,028)	(7,779)
Prepaid expenses and other assets	(47,848)	(7,971)
Accounts payable	14,047	(23,821)
Accrued expenses and other liabilities	83,643	(14,562)
Accrued restructuring expense	(1,058)	(2,892)
Deferred revenues	(1,199)	(7,131)
Net cash provided by operating activities	447,345	25,723
Cash flows from investing activities:
Purchases of marketable securities	(377,667)	(470,077)
Maturities of marketable securities	168,882	332,316
Expenditures for property and equipment	(28,866)	(27,892)
(Increase) decrease in restricted cash and cash equivalents (VIE)	(16,865)	8,397
Investment in CRISPR Series B preferred stock	0	(3,075)
Decrease (increase) in other assets	388	(159)
Net cash used in investing activities	(254,128)	(160,490)
Cash flows from financing activities:
Issuances of common stock under benefit plans	147,887	33,702
Payments on revolving credit facility	(300,000)	0
Advance from collaborator	7,500	0
Payments on capital lease obligations	(10,637)	(7,538)
Payments on construction financing lease obligation	(238)	(209)
Repayments of advanced funding	(2,044)	0
Net cash (used in) provided by financing activities	(157,532)	25,955
Effect of changes in exchange rates on cash	3,500	(90)
Net increase (decrease) in cash and cash equivalents	39,185	(108,902)
Cash and cash equivalents—beginning of period	1,183,945	714,768
Cash and cash equivalents—end of period	1,223,130	605,866
Supplemental disclosure of cash flow information:
Cash paid for interest	35,003	41,325
Cash paid for income taxes	2,218	1,237
Capitalization of costs related to construction financing lease obligation	38,930	0
Issuances of common stock from employee benefit plans receivable	$ 188	$ 161