CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities:
Net income (loss)	$ 279,862	$ (168,317)
Adjustments to reconcile net income (loss) to net cash used in by operating activities:
Depreciation and amortization	27,162	23,156
Non-cash compensation expense	63,385	40,561
Other non-cash charges and expenses, net	21,293	2,121
Changes in assets and liabilites
(Increase) decrease in Sanofi and trade accounts receivable	(498,236)	4,933
(Increase) decrease in prepaid expenses and other assets	(61,892)	3,425
Decrease in deferred revenue	(28,605)	(32,498)
Increase in accounts payable, accrued expenses and other liabilities	29,231	35,254
Total adjustments	(447,662)	76,952
Net cash used in operating activities	(167,800)	(91,365)
Cash flows from investing activities:
Purchases of marketable securities	(398,253)	(115,538)
Sales or maturities of marketable securities	260,770	324,530
Increase in restricted cash and marketable securities	(518)	(685)
Capital expenditures	(34,175)	(45,928)
Net cash (used in) provided by investing activities	(172,176)	162,379
Cash flows from financing activities:
Payments in connection with facility and capital lease obligations	(1,601)	(1,010)
Net proceeds from issuances of Common Stock	48,440	40,135
Payments in connection with Common Stock tendered for employee tax obligations	(71,475)	(16,316)
Net cash (used in) provided by financing activities	(24,636)	22,809
Net (decrease) increase in cash and cash equivalents	(364,612)	93,823
Cash and cash equivalents at beginning of period	483,610	112,572
Cash and cash equivalents at end of period	$ 118,998	$ 206,395