CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 327,556	$ 279,862
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	29,912	27,162
Non-cash compensation expense	143,217	63,385
Non-cash interest expense	17,316	17,009
Other non-cash charges and expenses, net	15,710	13,636
Deferred taxes	82,890
Changes in assets and liabilites
Increase in Sanofi and trade accounts receivable	(299,704)	(498,236)
Increase in prepaid expenses and other assets	(84,109)	(71,244)
Decrease in deferred revenue	(20,815)	(28,605)
(Decrease) increase in accounts payable, accrued expenses and other liabilities	94,894	29,231
Total adjustments	(20,689)	(447,662)
Net cash provided by (used in) operating activities	306,867	(167,800)
Cash flows from investing activities:
Purchases of marketable securities	(477,312)	(398,253)
Sales or maturities of marketable securities	319,152	260,770
Purchase of restricted cash and marketable securities		(518)
Capital expenditures	(87,347)	(34,175)
Net cash used in by investing activities	(245,507)	(172,176)
Cash flows from financing activities:
Payments in connection with facility and capital lease obligations	(1,625)	(1,601)
Proceeds from issuance of Common Stock	41,718	48,440
Payments in connection with Common Stock tendered for employee tax obligations	(166,358)	(71,475)
Excess tax benefit from stock-based compensation	97,840
Net cash used in financing activities	(28,425)	(24,636)
Net increase (decrease) in cash and cash equivalents	32,935	(364,612)
Cash and cash equivalents at beginning of period	230,276	483,610
Cash and cash equivalents at end of period	$ 263,211	$ 118,998