Consolidated Balance Sheets (Parentheticals) - USD ($)
Sep. 30, 2016
Dec. 31, 2015
Current assets:    
Allowance for doubtful accounts $ 1,507,016 $ 1,627,315
Customer relationships and other intangible assets, accumulated amortization $ 38,680,343 $ 26,785,810
Stockholders' equity:    
Common stock, par value (in usd per share) $ 0.0001 $ 0.0001
Common stock, shares authorized (in shares) 100,000,000 100,000,000
Common stock, shares issued (in shares) 30,351,479 29,765,525
Common stock, shares outstanding (in shares) 28,635,197 29,727,588
Treasury stock, shares (in shares) 1,716,282 37,937