(4) Fair Value Measurements (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash equivalents:
Total cash equivalents	$ 4,285,309	$ 8,129,960
Marketable securities:
Marketable securities, fair value, ending	10,530,942	21,505,410
Total assets measured at fair value	14,816,251	29,635,370
Fair Value, Inputs, Level 1 | Money Market Funds
Cash equivalents:
Total cash equivalents	4,285,309	8,129,960
Marketable securities:
Total assets measured at fair value	4,285,309	8,129,960
Fair Value, Inputs, Level 1 | Corporate Debt Securities Member
Marketable securities:
Marketable securities, fair value, ending	0	0
Total assets measured at fair value	0	0
Fair Value, Inputs, Level 1 | Auction Rate Securities Member
Marketable securities:
Marketable securities, fair value, ending		0
Total assets measured at fair value		0
Fair Value, Inputs, Level 2 | Money Market Funds
Cash equivalents:
Total cash equivalents	0	0
Marketable securities:
Total assets measured at fair value	0	0
Fair Value, Inputs, Level 2 | Corporate Debt Securities Member
Marketable securities:
Marketable securities, fair value, ending	10,530,942	20,894,328
Total assets measured at fair value	10,530,942	20,894,328
Fair Value, Inputs, Level 2 | Auction Rate Securities Member
Marketable securities:
Marketable securities, fair value, ending		0
Total assets measured at fair value		0
Level 3 Member | Money Market Funds
Cash equivalents:
Total cash equivalents	0	0
Marketable securities:
Total assets measured at fair value		0
Level 3 Member | Corporate Debt Securities Member
Marketable securities:
Marketable securities, fair value, ending	0	0
Total assets measured at fair value	0	0
Level 3 Member | Auction Rate Securities Member
Marketable securities:
Marketable securities, fair value, ending	$ 0	$ 611,082	$ 578,643