Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net income (loss)		$ 111,897,852	$ 111,335,817	$ 325,136,888	$ 331,608,542
Less: Allocated to participating securities		1,389,659		3,699,548
Net Income available to common shareholders		$ 110,508,193		$ 321,437,340
Basic weighted average shares outstanding (in shares)		251,075,859		252,811,950
Net Income per share - Basic (in dollars per share)	[1]	$ 0.44	$ 0.42	$ 1.27	$ 1.23
Reallocation of undistributed earnings		$ 6,051		$ 15,389
Net Income available to common shareholders - Diluted		$ 110,514,244		$ 321,452,729
Additional weighted average dilutive common stock equivalents (in shares)		1,503,123		1,455,901
Diluted weighted average shares outstanding (in shares)		252,578,982		254,267,851
Diluted (in dollars per share)	[1]	$ 0.44	$ 0.42	$ 1.26	$ 1.22
Shares related to stock plans not included in diluted average common shares outstanding because their effect would be anti-dilutive (in shares)		3,054		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.