Earnings Per Share (Schedule of Earnings Per Share, Basic And Diluted) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerators [Abstract]
Numerator for both basic and diluted EPS, net income	$ 72,336,883	$ 55,520,961	$ 217,629,700	$ 153,048,925
Denominators [Abstract]
Denominator for basic EPS, weighted-average shares outstanding	145,484,717	143,697,760	145,191,648	143,160,402
Potentially dilutive shares resulting from stock plans	953,259	821,140	1,176,808	655,639
Denominator for diluted EPS	146,437,976	144,518,900	146,368,456	143,816,041
Shares related to stock plans not included in diluted average common shares outstanding because their effect would be anti-dilutive	3,849,424	3,220,980	1,474,557	3,573,418