SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Sep. 30, 2015	[1]	Jun. 30, 2015	[1]	Mar. 31, 2015	[1]	Dec. 31, 2014	[1]	Sep. 30, 2014	[1]	Jun. 30, 2014	[1]	Mar. 31, 2014	[1]	Dec. 31, 2013	[1]	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Net Income
Basic earnings per share	$ 150,694		$ 112,992		$ 122,669		$ 46,218		$ 112,200		$ 71,925		$ 73,300		$ 83,397		$ 432,573	$ 340,822	$ 350,224
Stock options																	0	0	0
Restricted stock																	0	0	0
Diluted earnings per share																	$ 432,573	$ 340,822	$ 350,224
Shares
Basic earnings per share (in shares)																	64,581,000	64,240,000	65,073,000
Stock options (in shares)																	61,000	239,000	354,000
Restricted stock (in shares)																	388,000	595,000	418,000
Diluted earnings per share (in shares)																	65,030,000	65,074,000	65,845,000
Per Share Amount
Basic earnings per share (in dollars per share)	$ 2.33		$ 1.75		$ 1.90		$ 0.72		$ 1.74		$ 1.12		$ 1.14		$ 1.30		$ 6.70	$ 5.31	$ 5.38
Stock options (in dollars per share)																	0.00	(0.01)	(0.03)
Restricted stock (in dollars per share)																	(0.05)	(0.06)	(0.03)
Diluted earnings per share (in dollars per share)	$ 2.32		$ 1.73		$ 1.89		$ 0.71		$ 1.72		$ 1.11		$ 1.13		$ 1.28		$ 6.65	$ 5.24	$ 5.32
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding stock options excluded in the calculation of earnings per share																	866,000	0	0

[1] The sum of the individual quarterly earnings per common share amounts may not agree with year-to-date earnings per common share as each quarterly computation is based on the weighted-average number of common shares outstanding during that period.