Segments - Allocation of Long-Lived Tangible Assets Based on Geography (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
US long-lived tangible assets	$ 6,782,077	$ 5,976,544
Other countries long-lived tangible assets	30,944,145	24,901,175
Total long-lived tangible assets	37,726,222	30,877,719
Argentina [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Other countries long-lived tangible assets	16,955,438	14,316,612
Brazil [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Other countries long-lived tangible assets	2,421,618	2,528,378
Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Other countries long-lived tangible assets	378,653	409,707
Venezuela [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Other countries long-lived tangible assets	8,455,816	7,192,073
Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Other countries long-lived tangible assets	$ 2,732,620	$ 454,405