Stockholders' Equity - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended			9 Months Ended			12 Months Ended
	Jun. 17, 2015	Jan. 31, 2018	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2015	Sep. 30, 2015	Mar. 07, 2018	Sep. 30, 2017	Mar. 10, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense			$ 16,600,000			$ 16,600,000
Weighted average period for unrecognized compensation expense expected to be recognized (in years)						2 years 3 months 22 days
Purchase of common stock (in shares)			2,871,016			2,871,016					2,845,866
Recognized compensation expense			$ 1,980,000		$ 1,637,000	$ 5,927,000	$ 3,945,000
Total intrinsic value of options exercised						$ 1,200,000	600,000
Weighted average fair value of options granted (in dollars per share)						$ 4.56
Aggregate intrinsic value of options outstanding			12,800,000			$ 12,800,000					$ 15,600,000
IDchecker
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Business combination, paid earnout shares issued (in shares)								137,306	81,182
Closing shares | IDchecker
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense					300,000	0	900,000
Common stock issued during acquisition (in shares)	712,790
Vesting period of shares received (in months)	27 months
Earnout shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense			$ 0		200,000	$ 400,000	300,000
Common stock trading period (in days)				10 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for unrecognized compensation expense expected to be recognized (in years)						2 years 6 months 15 days
RSUs outstanding (in shares)			2,475,664			2,475,664					2,357,021
Recognized compensation expense			$ 1,300,000		1,200,000	$ 3,900,000	3,000,000
Unrecognized compensation expense			12,500,000			12,500,000
Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense			2,600,000			$ 2,600,000
Weighted average period for unrecognized compensation expense expected to be recognized (in years)						2 years 1 month 2 days
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for unrecognized compensation expense expected to be recognized (in years)						2 years 3 months 4 days
Recognized compensation expense			300,000		300,000	$ 900,000	800,000
Unrecognized compensation expense			$ 1,500,000			$ 1,500,000
2012 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)												9,500,000
Purchase of common stock (in shares)			1,841,450			1,841,450
Number of common stock reserved for future grants (in shares)			1,503,739			1,503,739
2012 Plan | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding (in shares)			2,032,826			2,032,826
2012 Plan | Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding (in shares)			2,042,817			2,042,817
Recognized compensation expense			$ 400,000		$ 100,000	$ 1,100,000	$ 100,000
Prior Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase of common stock (in shares)			1,029,566			1,029,566
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)										1,000,000
Shares outstanding under ESPP			0			0
ESPP, discount rate		15.00%
Recognized compensation expense			$ 82,000			$ 82,000
Director Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock reserved for future grants (in shares)			445,733			445,733
Director Plan | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)												1,500,000
Purchase of common stock (in shares)			442,838			442,838