Net Income (Loss) Per Share Data - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2017	Nov. 05, 2014
Earnings Loss Per Share [Line Items]
Weighted average diluted shares outstanding excluded outstanding stock options		500,000	300,000
Accelerated Share Repurchase Program [Member]
Earnings Loss Per Share [Line Items]
Maximum payments for repurchase of common stock				$ 25,300,000
Maximum [Member]
Earnings Loss Per Share [Line Items]
Weighted average diluted shares outstanding excluded outstanding stock options	100,000