GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
CONDENSED CONSOLIDATING STATEMENTS OF INCOME
Operating revenues	$ 566,110	$ 659,694	$ 883,052	$ 1,056,585	$ 985,038	$ 952,087	$ 893,430	$ 889,152	$ 3,165,441	$ 3,719,707	$ 3,387,614
Operating costs and other									2,489,691	2,664,920	2,430,953
Operating income from continuing operations	(16,021)	132,780	227,172	331,819	263,502	271,912	255,342	264,031	675,750	1,054,787	956,661
Other income, net									4,933	46,181	163,765
Interest expense									(15,036)	(4,654)	(6,129)
Income (loss) from continuing operations before income taxes									665,647	1,096,314	1,114,297
Income tax provision									243,375	387,548	392,844
Income (loss) from continuing operations	(21,208)	90,887	149,536	203,057	168,705	192,290	174,589	173,182	422,272	708,766	721,453
Income from discontinued operations before income taxes									(124)	2,758	14,701
Income tax provision (benefit)									(77)	2,805	(485)
Income (loss) from discontinued operations									(47)	(47)	15,186
NET INCOME (LOSS)	$ (21,214)	$ 90,860	$ 149,537	$ 203,042	$ 168,688	$ 192,279	$ 174,570	$ 173,182	422,225	708,719	736,639
Eliminations
CONDENSED CONSOLIDATING STATEMENTS OF INCOME
Operating revenues									(75)	(152)	(67)
Operating costs and other									(3,104)	(4,300)	(1,310)
Operating income from continuing operations									3,029	4,148	1,243
Other income, net									(3,029)	(4,148)	(1,288)
Interest expense											45
Equity in net income (loss) of subsidiaries									(417,933)	(719,825)	(778,465)
Income (loss) from continuing operations before income taxes									(417,933)	(719,825)	(778,465)
Income (loss) from continuing operations									(417,933)	(719,825)	(778,465)
NET INCOME (LOSS)									(417,933)	(719,825)	(778,465)
Guarantor/Parent | Reportable Legal Entities
CONDENSED CONSOLIDATING STATEMENTS OF INCOME
Operating costs and other									10,875	10,763	12,775
Operating income from continuing operations									(10,875)	(10,763)	(12,775)
Other income, net										57	20
Other income, net									(91)
Interest expense									(159)	(42)	(83)
Equity in net income (loss) of subsidiaries									429,140	715,157	745,105
Income (loss) from continuing operations before income taxes									418,015	704,409	732,267
Income tax provision									(4,210)	(4,310)	(4,372)
Income (loss) from continuing operations									422,225	708,719	736,639
NET INCOME (LOSS)									422,225	708,719	736,639
Issuer Subsidiary | Reportable Legal Entities
CONDENSED CONSOLIDATING STATEMENTS OF INCOME
Operating revenues									2,735,864	3,325,039	2,998,299
Operating costs and other									2,037,464	2,291,775	2,063,737
Operating income from continuing operations									698,400	1,033,264	934,562
Other income, net									7,522	48,108	164,170
Interest expense									(8,955)	(3,049)	(4,776)
Equity in net income (loss) of subsidiaries									(11,207)	4,668	33,360
Income (loss) from continuing operations before income taxes									685,760	1,082,991	1,127,316
Income tax provision									258,660	370,723	383,881
Income (loss) from continuing operations									427,100	712,268	743,435
NET INCOME (LOSS)									427,100	712,268	743,435
Non-Guarantor Subsidiaries | Reportable Legal Entities
CONDENSED CONSOLIDATING STATEMENTS OF INCOME
Operating revenues									429,652	394,820	389,382
Operating costs and other									444,456	366,682	355,751
Operating income from continuing operations									(14,804)	28,138	33,631
Other income, net									531	2,164	863
Interest expense									(5,922)	(1,563)	(1,315)
Income (loss) from continuing operations before income taxes									(20,195)	28,739	33,179
Income tax provision									(11,075)	21,135	13,335
Income (loss) from continuing operations									(9,120)	7,604	19,844
Income from discontinued operations before income taxes									(124)	2,758	14,701
Income tax provision (benefit)									(77)	2,805	(485)
Income (loss) from discontinued operations									(47)	(47)	15,186
NET INCOME (LOSS)									$ (9,167)	$ 7,557	$ 35,030