Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended								9 Months Ended		12 Months Ended
	Dec. 31, 2012 Investment	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Segment Investment	Dec. 31, 2011	Mar. 31, 2011
Summary Of Significant Accounting Policies [Line Items]
Royalty revenue	$ 9,104,000	$ 3,981,000	$ 3,865,000	$ 3,482,000	$ 4,051,000	$ 2,889,000	$ 3,295,000	$ 2,756,000	$ 10,235,194	$ 9,573,770	$ 20,432,348		$ 12,329,627
Revenue from sponsored research and development projects under agreements with the National Institutes of Health											803,000
Revenue from sponsored research and development projects									1,466,000	1,102,000			1,346,000
Marketable securities, average remaining contractual maturity period					9 months 27 days				9 months 27 days			9 months 27 days
Number of debt securities in unrealized loss positions	7										7
Debt securities in unrealized loss positions, total unrealized loss	1,000										1,000
Debt securities in unrealized loss positions, total fair market value	2,667,000										2,667,000
Reserves for excess and obsolete inventory	154,000				149,000			50,000	149,000	50,000	154,000	149,000	50,000
Depreciation expense of property and equipment									1,117,000	1,141,000	2,492,000		1,496,000
Stock options, outstanding	2,315,090				2,823,400				2,823,400	2,566,450	2,315,090	2,823,400
Stock options, weighted average exercise price	$ 4.20				$ 4.05				$ 4.05	$ 4.08	$ 4.20	$ 4.05
Common stock excluded from calculation of diluted earnings per share									2,823,400	1,771,100	1,296,700		2,580,600
Number of operating segment											1
Amortization expense									158,000	134,000	1,017,000	179,000
Expected amortization expense in 2013	1,000,000										1,000,000
Expected amortization expense in 2014	1,000,000										1,000,000
Expected amortization expense in 2015	1,000,000										1,000,000
Expected amortization expense in 2016	1,000,000										1,000,000
Expected amortization expense in 2017	1,000,000										1,000,000
Expected dividend yield											0
Non-Executive Employees
Summary Of Significant Accounting Policies [Line Items]
Estimated annual forfeiture rates											8.00%
Awards Granted to Executive Level Employees
Summary Of Significant Accounting Policies [Line Items]
Estimated annual forfeiture rates											3.00%
Assets Held under Capital Leases
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense of property and equipment										82,000			82,000
Minimum
Summary Of Significant Accounting Policies [Line Items]
Marketable securities, minimum original maturity term	90 days										90 days
Long-term marketable securities, minimum original maturity term	1 year										1 year
Bristol Myers Squibb Company
Summary Of Significant Accounting Policies [Line Items]
Royalty revenue									8,769,000		14,753,000		10,251,000
Qualifying Therapeutic Discovery Project Program
Summary Of Significant Accounting Policies [Line Items]
Revenue from sponsored research and development projects										$ 733,000			$ 733,000