Income Taxes - Reconciliation of Provision to Federal Statutory Rate (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Tax provision at U.S. statutory rate		$ (25,352)	$ (13,185)	$ (7,016)
State income taxes, net of federal tax effect		(1,349)	(931)	(1,973)
Valuation allowance		(208)	109,277	7,994
Non-deductible executive compensation			(105)	(1,242)
Tax credits		1,741	186	305
Unrealized gains		1,558
Unrecognized tax benefits		3,570	706	101
Other		(2,716)	(1,490)	(1,743)
Income tax benefit (provision)	$ 96,800	$ (22,756)	$ 94,458	$ (3,574)