CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income (loss)	$ (86,839)	$ (162,261)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	4,298	2,492
Stock-based compensation	21,853	18,573
Amortization of convertible senior notes discount and debt issuance costs	6,300	5,581
Amortization of finite-lived intangible assets	10,441
Changes in fair value of liability for contingent consideration	5,952	56,392
Non-cash milestone payment received		(1,462)
Realized losses on sale of marketable securities	94
Changes in operating assets and liabilities:
Accounts receivable	(52,194)
Receivable from collaboration partners	(11,981)	(3,780)
Inventory	(14,205)
Prepaid expenses and other current assets	10,631	25
Other assets	(817)	(3,029)
Accounts payable	2,558	84
Accrued liabilities	(3,927)	(10,119)
Accrued clinical trials and related expenses	(1,825)	5,886
Accrued compensation	(7,084)	(3,190)
Deferred revenue	216
Lease termination exit costs liability		(3,177)
Other current liabilities	1,044
Other liabilities	961	11,008
Net cash (used in) provided by operating activities	(114,524)	(86,977)
Cash flows from investing activities:
Purchases of marketable securities	(276,270)	(124,070)
Sales of marketable securities	16,182	104,764
Maturities of marketable securities	165,956	131,516
Capital expenditures	(10,696)	(16,063)
Net cash (used in) provided by investing activities	(104,828)	96,147
Cash flows from financing activities:
Repurchases of restricted stock awards	(417)	(124)
Net proceeds from issuances of common stock	389,602	25,608
Payment for redemption of convertible senior notes	(9)
Net cash provided by financing activities	389,176	25,484
Net increase (decrease) in cash and cash equivalents	169,824	34,654
Cash and cash equivalents at beginning of period	153,244	171,552
Cash and cash equivalents at end of period	323,068	206,206
Supplemental cash flow data
Cash paid during the period for income taxes	34	42
Cash paid during the period for interest	$ 4,600	$ 4,600