Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)	$ (72,835)	$ (21,200)	$ 21,205	$ 16,002	$ (27,596)	$ 90,872	$ 153,543	$ 203,608	$ (56,828)	$ 420,427	$ 706,563
Other comprehensive income, net of income taxes:
Unrealized appreciation (depreciation) on securities, net of income taxes of $1.7 million at September 30, 2016, ($50.6) million at September 30, 2015 and ($15.5) million at September 30, 2014									2,772	(80,217)	(19,006)
Reclassification of realized (gains) losses in net income, net of income taxes of $0.6 million at September 30, 2016 and ($17.5) million at September 30, 2014									926		(27,737)
Minimum pension liability adjustments, net of income taxes of $1.4 million at September 30, 2016, ($2.5) million at September 30, 2015 and ($1.5) million at September 30, 2014									(2,525)	(4,286)	(2,661)
Other comprehensive income (loss)									1,173	(84,503)	(49,404)
Comprehensive income (loss)									$ (55,655)	$ 335,924	$ 657,159