Income Taxes (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Taxes
Provisions for income taxes	$ 823,831	$ 304,168
Effective tax rate (as a percent)	35.60%		36.80%
Increase in the effective tax rate due to higher U.S. state tax expense (as a percent)	4.10%	4.80%
Decrease in effective tax rate due to domestic production activities deduction (as a percent)	2.70%	3.70%