Income Taxes Computed at Federal Statutory Rate (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Income Taxes [Line Items]
Income from continuing operations before taxes	$ (44,115)	$ (16,618)	$ 89,289	$ 32,843	$ (23,686)	$ (11,952)	$ 70,796	$ 14,669	$ 61,399	$ 49,827	$ 42,565
Provision for income taxes:
Tax at Federal statutory rate									21,490	17,440	14,898
Impact of Partnership loss not subject to federal income taxes									628	97	697
State taxes net of federal benefit									3,310	3,192	2,801
Permanent differences									57	37	28
Change in valuation allowance										(658)	(14)
Change in unrecognized tax benefit									(113)	55	(1,669)
Other									(57)	(242)	(165)
Income tax expense									$ 25,315	$ 19,921	$ 16,576