Income Tax (Detail) - Reconciliation from expected federal tax expense of 35% to consolidated effective income (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012	Sep. 30, 2011	Sep. 30, 2010
Expected federal income tax expense (benefit)	$ 8,868	$ 16,871	$ (21,452)	$ (22,847)
Increases (decreases) in income taxes resulting from
State income tax expense (benefit), net of federal income tax effect	974	1,209	(2,044)	(2,166)
Deferred adjustment for charter conversion	0	1,180	0	0
Tax exempt income	(87)	(480)	(374)	(408)
Other, net	11	610	198	(548)
Total	$ 9,766	$ 19,390	$ (23,672)	$ (25,969)
Effective tax rate	38.54%	40.23%	38.62%	39.78%