Operating Leases and Subleases (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 Y sqft count building	Dec. 31, 2010	Dec. 31, 2009
Operating Leases and Subleases
Number of lease terms	2
Additional lease period (in years)	5
Number of buildings	2
Area of building one in South San Francisco, California (in square feet)	110,000
Area of building two in South San Francisco, California (in square feet)	40,000
Future minimum lease payments
2012	$ 5,429,000
2013	5,029,000
2014	4,859,000
2015	5,005,000
2016	5,156,000
Thereafter	18,806,000
Total	44,284,000
Expenses and income associated with operating leases
Rent expense	6,702,000	6,779,000	6,559,000
Sublease income, net	(637,000)	(622,000)	(580,000)
Future minimum rental receivable under non-cancelable sublease	$ 200,000