Segment information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Number of business segments									2
Number of business units									2
External revenue									$ 281,888	$ 273,384	$ 286,171
Intersegment revenue (expense)									0	0	0
Research and development									120,226	124,832	89,295
Interest revenue									134	105	832
Interest expense									(6)	0	0
Depreciation and amortization									11,197	9,355	5,990
Net income (loss)	16,104	6,617	7,632	(6,829)	28,657	1,549	14,210	(21,397)	23,524	23,019	51,698
In-process research and development assets	41,800				51,400				41,800	51,400	51,400
Goodwill	5,502				5,502				5,502	5,502	5,502
Total assets	564,230				546,864				564,230	546,864	500,319
Expenditures for long-lived assets									53,845	54,026	22,101
Biodefense [Member]
Segment Reporting Information [Line Items]
External revenue									276,469	251,037	282,727
Intersegment revenue (expense)									0	0	0
Research and development									68,579	57,833	52,191
Interest revenue									0	0	0
Interest expense									0	0	0
Depreciation and amortization									8,951	6,213	4,584
Net income (loss)									94,865	86,836	113,249
In-process research and development assets	0				0				0	0	0
Goodwill	0				0				0	0	0
Total assets	354,010				290,302				354,010	290,302	216,529
Expenditures for long-lived assets									52,957	52,326	21,728
Biosciences [Member]
Segment Reporting Information [Line Items]
External revenue									5,419	22,347	3,444
Intersegment revenue (expense)									0	0	0
Research and development									44,588	61,566	32,895
Interest revenue									0	0	0
Interest expense									0	0	0
Depreciation and amortization									2,147	3,070	1,333
Net income (loss)									(63,928)	(56,438)	(53,676)
In-process research and development assets	41,800				51,400				41,800	51,400	51,400
Goodwill	5,502				5,502				5,502	5,502	5,502
Total assets	56,148				92,321				56,148	92,321	99,754
Expenditures for long-lived assets									810	1,608	373
All Other [Member]
Segment Reporting Information [Line Items]
External revenue											0
Intersegment revenue (expense)									0	0	0
Research and development									7,059	5,433	4,209
Interest revenue									134	105	832
Interest expense									(6)	0	0
Depreciation and amortization									99	72	73
Net income (loss)									(7,413)	(7,379)	(7,875)
In-process research and development assets	0				0				0	0	0
Goodwill	0				0				0	0	0
Total assets	154,072				164,241				154,072	164,241	184,036
Expenditures for long-lived assets									$ 78	$ 92	$ 0