Current and Deferred Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred Income Tax Assets And Liabilities
Income before income taxes	$ 3,288	$ 28,670
Current tax expense	1,589	1,228
Deferred tax (benefit) expense	(616)	8,712
Deferred tax benefit - impact of tax reform		(11,452)
Total deferred tax benefit	(616)	(2,740)
Total tax expense (benefit)	$ 973	$ (1,512)