Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Balance Type:	na
Period Type:	duration

Stockholders' Equity - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Nov. 06, 2015	Nov. 05, 2014
Stockholders Equity [Line Items]
Payments for repurchase of common stock	$ 4,702,000
Common stock repurchased, Shares	196,190
Stock repurchased average price per share	$ 23.97
Remaining amount available for repurchases of shares		$ 25,300,000
Accelerated Share Repurchase Program [Member]
Stockholders Equity [Line Items]
Maximum payments for repurchase of common stock			$ 20,000,000	$ 30,000,000