Nature of Operations and Summary of Significant Accounting Policies - Potentially Dilutive Common Shares Excluded from Calculation of Net Loss per Share (Detail) - shares shares in Thousands	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potentially dilutive common shares outstanding (in shares)	5,848	6,170
IDchecker | Closing shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potentially dilutive common shares outstanding (in shares)	0	464
IDchecker | Earnout shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potentially dilutive common shares outstanding (in shares)	0	164
RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potentially dilutive common shares outstanding (in shares)	2,786	2,435
Stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potentially dilutive common shares outstanding (in shares)	3,062	3,107