Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Basic Earnings Per Share
Net Income		$ 117,092,602	$ 111,897,852	$ 204,224,370	$ 325,136,888
Less: Dividends and undistributed earnings allocated to participating securities		1,697,281	1,389,659	2,906,048	3,699,548
Net (Loss) Income available to common shareholders		$ 115,395,321	$ 110,508,193	$ 201,318,322	$ 321,437,340
Basic weighted average shares outstanding (in shares)		241,898,117	251,075,859	243,240,699	252,811,950
Net (Loss) Income per share - Basic (in dollars per share)	[1]	$ 0.48	$ 0.44	$ 0.83	$ 1.27
Earnings Per Share, Diluted [Abstract]
Allocation of Net (Loss) Income used in basic computation		$ 115,395,321	$ 110,508,193	$ 201,318,322	$ 321,437,340
Reallocation of undistributed earnings		4,742	6,051	6,731	15,389
Net (Loss) Income available to common shareholders - Diluted		$ 115,400,063	$ 110,514,244	$ 201,325,053	$ 321,452,729
Number of shares used in basic computation		241,898,117	251,075,859	243,240,699	252,811,950
Additional weighted average dilutive common stock equivalents (in shares)		918,950	1,503,123	1,026,916	1,455,901
Diluted weighted average shares outstanding (in shares)		242,817,067	252,578,982	244,267,615	254,267,851
Net (Loss) Income per share - Diluted (in dollars per share)	[1]	$ 0.48	$ 0.44	$ 0.82	$ 1.26
Shares related to stock plans not included in diluted average common shares outstanding because their effect would be anti-dilutive (in shares)		412,775	3,054	412,775	170,386

[1] (1) Earnings Per Share has been adjusted to exclude the portion of net income allocated to participating securities as a result of share-based payment awards.