Guarantor and Non-Guarantor Financial Information - Statement of Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS
Operating revenue	$ 498,564	$ 366,486	$ 1,272,437	$ 1,292,524
Operating costs and other	526,592	379,742	1,415,301	1,225,489
Operating income (loss) from continuing operations	(28,028)	(13,256)	(142,864)	67,035
Other income (expense), net	789	1,312	3,678	3,236
Interest expense	(6,364)	(6,407)	(17,503)	(16,652)
Income (loss) from continuing operations before income taxes	(33,603)	(18,351)	(156,689)	53,619
Income tax provision	(10,478)	2,842	(50,537)	33,740
Income (loss) from continuing operations	(23,125)	(21,193)	(106,152)	19,879
Income (loss) from discontinued operations before income taxes	3,223	2,193	2,705	2,241
Income tax provision (benefit)	1,897	2,200	2,233	6,113
Income (loss) from discontinued operations	1,326	(7)	472	(3,872)
NET INCOME (LOSS)	(21,799)	(21,200)	(105,680)	16,007
Eliminations
CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS
Operating revenue	(18)	(20)	(51)	(53)
Operating costs and other	(216)	(290)	(677)	(1,093)
Operating income (loss) from continuing operations	198	270	626	1,040
Other income (expense), net	(198)	(270)	(626)	(1,040)
Equity in net income (loss) of subsidiaries	19,595	26,368	110,053	1,769
Income (loss) from continuing operations before income taxes	19,595	26,368	110,053	1,769
Income (loss) from continuing operations	19,595	26,368	110,053	1,769
NET INCOME (LOSS)	19,595	26,368	110,053	1,769
Guarantor/Parent | Reportable Legal Entities
CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS
Operating costs and other	3,364	3,712	10,124	9,573
Operating income (loss) from continuing operations	(3,364)	(3,712)	(10,124)	(9,573)
Other income (expense), net	(4)	16	(3)	(235)
Interest expense	(87)	(62)	(260)	(186)
Equity in net income (loss) of subsidiaries	(19,510)	(18,572)	(99,179)	22,042
Income (loss) from continuing operations before income taxes	(22,965)	(22,330)	(109,566)	12,048
Income tax provision	(1,166)	(1,130)	(3,886)	(3,959)
Income (loss) from continuing operations	(21,799)	(21,200)	(105,680)	16,007
NET INCOME (LOSS)	(21,799)	(21,200)	(105,680)	16,007
Issuer Subsidiary | Reportable Legal Entities
CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS
Operating revenue	439,227	315,077	1,103,877	1,103,361
Operating costs and other	463,220	314,620	1,218,266	1,003,369
Operating income (loss) from continuing operations	(23,993)	457	(114,389)	99,992
Other income (expense), net	2,052	1,290	4,885	2,680
Interest expense	(5,294)	(5,597)	(15,151)	(15,587)
Equity in net income (loss) of subsidiaries	(85)	(7,796)	(10,874)	(23,811)
Income (loss) from continuing operations before income taxes	(27,320)	(11,646)	(135,529)	63,274
Income tax provision	(7,360)	7,230	(37,320)	42,114
Income (loss) from continuing operations	(19,960)	(18,876)	(98,209)	21,160
NET INCOME (LOSS)	(19,960)	(18,876)	(98,209)	21,160
Non-Guarantor Subsidiaries | Reportable Legal Entities
CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS
Operating revenue	59,355	51,429	168,611	189,216
Operating costs and other	60,224	61,700	187,588	213,640
Operating income (loss) from continuing operations	(869)	(10,271)	(18,977)	(24,424)
Other income (expense), net	(1,061)	276	(578)	1,831
Interest expense	(983)	(748)	(2,092)	(879)
Income (loss) from continuing operations before income taxes	(2,913)	(10,743)	(21,647)	(23,472)
Income tax provision	(1,952)	(3,258)	(9,331)	(4,415)
Income (loss) from continuing operations	(961)	(7,485)	(12,316)	(19,057)
Income (loss) from discontinued operations before income taxes	3,223	2,193	2,705	2,241
Income tax provision (benefit)	1,897	2,200	2,233	6,113
Income (loss) from discontinued operations	1,326	(7)	472	(3,872)
NET INCOME (LOSS)	$ 365	$ (7,492)	$ (11,844)	$ (22,929)