Stock-based Compensation (Details 1) (USD $)	6 Months Ended
	Jun. 30, 2012 Y	Jun. 30, 2011
Summary of information related to stock options
Number of Options Outstanding, beginning balance	1,682,911
Weighted Average Exercise Price, beginning balance	$ 11.82
Number of Options Outstanding, Granted	258,600	102,700
Number of Options Outstanding, Exercised	(376,211)
Number of Options Outstanding, Forfeited	(78,958)
Number of Options Outstanding, ending balance	1,486,342
Weighted Average Exercise Price, ending balance	$ 17.25
Weighted Average Remaining Contractual Term (years), ending balance	7.91
Aggregate Intrinsic Value, ending balance	$ 22,443,987
Number of Options Outstanding Vested, ending balance	714,097
Weighted Average Exercise Price Vested, ending balance	$ 4.76
Weighted Average Remaining Contractual Term Vested, ending balance	6.90
Aggregate Intrinsic Value Vested, ending balance	17,522,120
Number of Options Outstanding Exercisable, ending balance	752,556
Weighted Average Exercise Price Exercisable, Ending balance	$ 4.64
Weighted Average Remaining Contractual Term Exercisable, ending balance	6.84
Aggregate Intrinsic Value Exercisable, ending balance	$ 18,295,189