Earnings Per Share (Schedule of Earnings Per Share, Basic And Diluted) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerators:
Numerator for both basic and diluted EPS, net income	$ 111,248,743	$ 97,556,741
Denominators:
Denominator for basic EPS, weighted-average shares outstanding (in shares)	274,759,516	287,408,900
Potentially dilutive shares resulting from stock plans (in shares)	2,749,912	4,070,938
Denominator for diluted EPS (in shares)	277,509,428	291,479,838
Shares related to stock plans not included in diluted average common shares outstanding because their effect would be anti-dilutive (in shares)	156,467	2,311