Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended									12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2014	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Basic Earnings Per Share from continuing operations
Income from continuing operations										$ 511,406	$ 603,064	$ 382,711
Less: Income from continuing operations allocated to participating securities										416	580	475
Income from continuing operations available to common shareholders										$ 510,990	$ 602,484	$ 382,236
Weighted average shares outstanding - basic										117,200	111,012	106,100
Income per share from continuing operations - basic										$ 4.36	$ 5.43	$ 3.60
Effect of dilutive shares										$ 0	$ 0	$ 0
Income from continuing operations available to common shareholders - diluted										$ 510,990	$ 602,484	$ 382,236
Dilutive shares										261	0	0
Weighted average shares outstanding - diluted										117,461	111,012	106,100
Income per share from continuing operations - diluted										$ 4.35	$ 5.43	$ 3.60
Basic Earnings Per Share from discontinued operations
Income from discontinued operations										$ 0	$ 0	$ 13,710
Less: Income from discontinued operations allocated to participating securities										0	0	12
Income from discontinued operations available to common shareholders										$ 0	$ 0	$ 13,698
Income per share from discontinued operations - basic										$ 0	$ 0	$ 0.13
Income from discontinued operations available to common shareholders, diluted										$ 0	$ 0	$ 13,698
Income per share from discontinued operations - diluted										$ 0	$ 0	$ 0.13
Earnings Per Share, Basic	$ 0.49	$ 0.68	$ 1.83	$ 1.38	$ 0.35	$ 0.64	$ 1.60	$ 2.89	$ 3.73	4.36	5.43	3.73
Earnings Per Share, Diluted	$ 0.49	$ 0.68	$ 1.82	$ 1.38	$ 0.35	$ 0.64	$ 1.60	$ 2.89		$ 4.35	$ 5.43	$ 3.73