Investments in Debt Securities (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 34,017,451	$ 20,745,938
Gross Unrealized Gain	4,637	15,479
Gross Unrealized Loss	(9,936)	(1,367)
Fair Value	34,012,152	20,760,050
Marketable securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,792,154	10,835,995
Gross Unrealized Gain	4,071	9,207
Gross Unrealized Loss	(2,675)	(7)
Fair Value	21,793,550	10,845,195
Marketable securities | U.S. Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,165,464	2,000,897
Gross Unrealized Gain	435	353
Gross Unrealized Loss	(630)	(7)
Fair Value	8,165,269	2,001,243
Marketable securities | Corporate and other debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,626,690	8,835,098
Gross Unrealized Gain	3,636	8,854
Gross Unrealized Loss	(2,045)
Fair Value	13,628,281	8,843,952
Long-term marketable securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,225,297	9,909,943
Gross Unrealized Gain	566	6,272
Gross Unrealized Loss	(7,261)	(1,360)
Fair Value	12,218,602	9,914,855
Long-term marketable securities | U.S. Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,599,415	5,198,264
Gross Unrealized Gain	466	2,747
Gross Unrealized Loss	(7,034)
Fair Value	11,592,847	5,201,011
Long-term marketable securities | Corporate and other debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	625,882	4,711,679
Gross Unrealized Gain	100	3,525
Gross Unrealized Loss	(227)	(1,360)
Fair Value	$ 625,755	$ 4,713,844