GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION - Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS
Operating revenue	$ 740,598	$ 564,087
Operating costs and other	686,309	560,478
Operating income from continuing operations	54,289	3,609
Other (expense) income, net	(44,573)	(3,608)
Interest expense	(4,720)	(5,773)
Income from continuing operations before income taxes	9,716	1
Income tax (benefit) provision	1,352	(500,641)
Income from continuing operations	8,364	500,642
Income (loss) from discontinued operations before income taxes	12,665	(519)
Income tax provision	2,070	17
Income (loss) from discontinued operations	10,595	(536)
Net income (loss)	18,959	500,106
Eliminations
CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS
Operating revenue	(24)	(16)
Operating costs and other	(269)	(205)
Operating income from continuing operations	245	189
Other (expense) income, net	(245)	(189)
Equity in net income (loss) of subsidiaries	(37,701)	(528,785)
Income from continuing operations before income taxes	(37,701)	(528,785)
Income from continuing operations	(37,701)	(528,785)
Net income (loss)	(37,701)	(528,785)
Guarantor/Parent | Reportable Legal Entities
CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS
Operating costs and other	2,766	4,089
Operating income from continuing operations	(2,766)	(4,089)
Other (expense) income, net	(1,036)	144
Equity in net income (loss) of subsidiaries	22,396	507,420
Income from continuing operations before income taxes	18,594	503,475
Income tax (benefit) provision	(365)	3,369
Income from continuing operations	18,959	500,106
Net income (loss)	18,959	500,106
Issuer Subsidiary | Reportable Legal Entities
CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS
Operating revenue	661,151	495,006
Operating costs and other	598,973	481,648
Operating income from continuing operations	62,178	13,358
Other (expense) income, net	(45,200)	(4,059)
Equity in net income (loss) of subsidiaries	15,305	21,365
Income from continuing operations before income taxes	32,283	30,664
Income tax (benefit) provision	5,159	(478,594)
Income from continuing operations	27,124	509,258
Net income (loss)	27,124	509,258
Non-Guarantor Subsidiaries | Reportable Legal Entities
CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS
Operating revenue	79,471	69,097
Operating costs and other	84,839	74,946
Operating income from continuing operations	(5,368)	(5,849)
Other (expense) income, net	1,908	496
Income from continuing operations before income taxes	(3,460)	(5,353)
Income tax (benefit) provision	(3,442)	(25,416)
Income from continuing operations	(18)	20,063
Income (loss) from discontinued operations before income taxes	12,665	(519)
Income tax provision	2,070	17
Income (loss) from discontinued operations	10,595	(536)
Net income (loss)	$ 10,577	$ 19,527