Earnings Per Share (Schedule of Earnings Per Share, Basic And Diluted) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 104,280,411	$ 111,248,743
Less: Allocated to participating securities	1,081,933	833,316
Net Income available to common shareholders	$ 103,198,478	$ 110,415,427
Basic weighted average shares outstanding	257,822,836	274,759,516
Basic (in dollars per share)	$ 0.40	$ 0.40
Reallocation of undistributed earnings	$ 3,813	$ 6,011
Net Income per share - Diluted	$ 103,202,291	$ 110,421,438
Additional dilutive common stock equivalents	1,282,396	2,749,912
Diluted weighted average shares outstanding	259,105,232	277,509,428
Diluted (in dollars per share)	$ 0.40	$ 0.40
Shares related to stock plans not included in diluted average common shares outstanding because their effect would be anti-dilutive	1,799,477	156,467