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Restatement - Summary of Basic and Diluted Net Income per Common Share Available to Common Shareholders (Detail) - $ / shares shares in Thousands	3 Months Ended												12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Line Items]
Net income per common share available to common shareholders - Basic	$ 0.35	$ 0.09	$ 0.38	$ 0.55	$ 0.66	$ (0.48)	$ 0.10	$ 0.97	$ 0.24	$ 0.67	$ 0.23	$ 0.28	$ 1.37	$ 1.34	$ 1.41
Shares used in computing net income per common share available to common shareholders - Basic													34,764	24,826	23,201
Net income per common share available to common shareholders - Diluted	$ 0.35	$ 0.09	$ 0.38	0.54	0.65	(0.48)	0.10	0.96	0.24	0.66	0.23	0.28	$ 1.36	$ 1.32	$ 1.40
Shares used in computing net income per common share available to common shareholders - Diluted													35,064	25,257	23,370
As Previously Reported
Earnings Per Share [Line Items]
Net income per common share available to common shareholders - Basic				0.80	1.04	(0.89)	0.20	2.00	0.49	1.40	0.48	0.62		$ 2.46	$ 3.01
Shares used in computing net income per common share available to common shareholders - Basic														13,516	10,919
Net income per common share available to common shareholders - Diluted				$ 0.55	$ 0.65	$ (0.89)	$ 0.10	$ 0.96	$ 0.23	$ 0.66	$ 0.23	$ 0.28		$ 1.32	$ 1.40
Shares used in computing net income per common share available to common shareholders - Diluted														25,171	23,386

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Earnings Per Share [Line Items]

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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