CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income (loss) - basic and diluted	$ 88,394	$ (105,952)
Adjustments to reconcile net income (loss) to net cash used in by operating activities:
Depreciation and amortization	17,833	14,880
Non-cash compensation expense	42,850	27,197
Other non-cash charges and expenses, net	13,373	832
Changes in assets and liabilities:
Increase in Sanofi and trade accounts receivable	(332,345)	(1,138)
(Increase) decrease in prepaid expenses and other assets	(10,643)	1,528
Decrease in deferred revenue	(17,669)	(20,554)
Increase in accounts payable, accrued expenses, and other liabilities	32,789	38,577
Total adjustments	(253,812)	61,322
Net cash used in operating activities	(165,418)	(44,630)
Cash flows from investing activities:
Purchases of marketable securities	(270,907)	(15,638)
Sales or maturities of marketable securities	171,881	216,631
Increase in restricted cash and marketable securities	(469)	(681)
Capital expenditures	(23,927)	(37,030)
Net cash (used in) provided by investing activities	(123,422)	163,282
Cash flows from financing activities:
Payments in connection with facility and capital lease obligations	(1,014)	(704)
Net proceeds from issuances of Common Stock	39,631	28,501
Payments in connection with Common Stock tendered for employee tax obligations	(61,444)	(4,709)
Net cash (used in) provided by financing activities	(22,827)	23,088
Net (decrease) increase in cash and cash equivalents	(311,667)	141,740
Cash and cash equivalents at beginning of period	483,610	112,572
Cash and cash equivalents at end of period	$ 171,943	$ 254,312