Current and Deferred Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Deferred Income Tax Assets And Liabilities
Income before income taxes	$ (13,970)	$ (16,618)	$ 142,819	$ 105,514
Current tax expense	(6,433)	(7,888)	51,339	34,550
Deferred tax expense	822	862	8,598	9,052
Total tax expense	$ (5,611)	$ (7,026)	$ 59,937	$ 43,602