Guarantor and Non-Guarantor financial information - Comprehensive Income (Loss) (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 COMPREHENSIVE INCOME (LOSS)
Net income (loss)	$ (21,799)	$ (21,200)	$ (105,680)	$ 16,007
Other comprehensive income (loss), net of income taxes:
Unrealized (appreciation) depreciation on securities, net	(6,899)	9,744	(4,994)	(2,719)
Unrealized depreciation on securities, net	(6,899)	9,744
Minimum pension liability adjustments, net	365	314	1,097	940
Other comprehensive income (loss)	(6,534)	10,058	(3,897)	(1,779)
Comprehensive income (loss)	(28,333)	(11,142)	(109,577)	14,228
Reportable Legal Entities \| Guarantor/Parent
CONSOLIDATED CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss)	(21,799)	(21,200)	(105,680)	16,007
Other comprehensive income (loss), net of income taxes:
Minimum pension liability adjustments, net	104	107	316	322
Other comprehensive income (loss)	104	107	316	322
Comprehensive income (loss)	(21,695)	(21,093)	(105,364)	16,329
Reportable Legal Entities \| Issuer Subsidiary
CONSOLIDATED CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss)	(19,960)	(18,876)	(98,209)	21,160
Other comprehensive income (loss), net of income taxes:
Unrealized (appreciation) depreciation on securities, net			(4,994)	(2,719)
Unrealized depreciation on securities, net	(6,899)	9,744
Minimum pension liability adjustments, net	261	207	781	618
Other comprehensive income (loss)	(6,638)	9,951	(4,213)	(2,101)
Comprehensive income (loss)	(26,598)	(8,925)	(102,422)	19,059
Reportable Legal Entities \| Non-Guarantor Subsidiaries
CONSOLIDATED CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss)	365	(7,492)	(11,844)	(22,929)
Other comprehensive income (loss), net of income taxes:
Comprehensive income (loss)	365	(7,492)	(11,844)	(22,929)
Eliminations
CONSOLIDATED CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss)	19,595	26,368	110,053	1,769
Other comprehensive income (loss), net of income taxes:
Comprehensive income (loss)	$ 19,595	$ 26,368	$ 110,053	$ 1,769

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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