Income Tax (Detail) - Income tax expense (USD $) In Thousands, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Dec. 31, 2012	Sep. 30, 2011	Sep. 30, 2010
Current tax expense (benefit)
Federal					$ 284					$ 9,149	$ (17,343)	$ (22,320)
State					654					1,337	(1,460)	(2,229)
Total current tax expense (benefit)					938					10,486	(18,803)	(24,549)
Deferred tax expense (benefit)
Federal					7,985					7,202	(3,248)	316
State					843					1,702	(1,621)	(1,736)
Total deferred tax expense (benefit)					8,828					8,904	(4,869)	(1,420)
Total tax expense (benefit) from continuing operations					9,766	1,893	(25,288)	(913)		19,390	(23,672)	(25,969)
Total tax expense from discontinued operations					0					0	6,549	1,581
Total tax expense (benefit)	$ 3,921	$ 3,516	$ 7,712	$ 4,241	$ 9,766				$ 636	$ 19,390	$ (17,123)	$ (24,388)