Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)	$ (22,532)	$ (21,799)	$ (48,818)	$ (35,063)	$ (72,835)	$ (21,200)	$ 21,205	$ 16,002	$ (128,212)	$ (56,828)	$ 420,427
Other comprehensive income (loss), net of income taxes:
Unrealized appreciation (depreciation) on securities, net of income taxes of ($0.5) million at September 30, 2017, $1.7 million at September 30, 2016 and ($50.6) million at September 30, 2015									(829)	2,772	(80,217)
Reclassification of realized losses in net income, net of income taxes of $0.6 million at September 30, 2016										926
Minimum pension liability adjustments, net of income taxes of $1.9 million at September 30, 2017, ($1.4) million at September 30, 2016 and ($2.5) million at September 30, 2015									3,333	(2,525)	(4,286)
Other comprehensive income (loss)									2,504	1,173	(84,503)
Comprehensive income (loss)									$ (125,708)	$ (55,655)	$ 335,924