Stock-Based Compensation Plans (Summary of Stock-based compensation expense recognized (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 2,162,434	$ 2,564,096	$ 7,757,051	$ 6,734,848
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	886,281	737,208	2,831,966	1,795,501
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 1,276,153	$ 1,826,888	$ 4,925,085	$ 4,939,347