Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Trade receivables, allowance for doubtful accounts	$ 8,347,300.39	$ 2,483,172.89
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	37,939,032	37,684,829
Treasury stock, shares	20,538,327	20,529,929
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0