Earnings Per Share (Schedule of Earnings Per Share, Basic And Diluted) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerators [Abstract]
Numerator for both basic and diluted EPS, net income	$ 76,726,746	$ 52,097,397	$ 145,292,817	$ 97,527,964
Denominators [Abstract]
Denominator for basic EPS, weighted-average shares outstanding	145,215,130	143,240,333	145,059,684	142,888,337
Potentially dilutive shares resulting from stock plans	1,284,363	770,292	1,558,905	649,655
Denominator for diluted EPS	146,499,493	144,010,625	146,618,589	143,537,992
Shares related to stock plans not included in diluted average common shares outstanding because their effect would be anti-dilutive	2,994,629	3,270,342	995,177	3,454,067