Revenue Recognition - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 19,983	$ 14,277	$ 37,666	$ 26,413
Deposits revenue
Disaggregation of Revenue [Line Items]
Total revenue	12,908	8,611	24,778	15,712
Identity verification revenue
Disaggregation of Revenue [Line Items]
Total revenue	7,075	5,666	12,888	10,701
Transferred at Point in Time | Deposits software and hardware
Disaggregation of Revenue [Line Items]
Total revenue	9,215	6,735	18,265	11,882
Transferred at Point in Time | Identity verification software and hardware
Disaggregation of Revenue [Line Items]
Total revenue	1,370	2,038	2,315	4,097
Transferred over Time | Deposits services and other
Disaggregation of Revenue [Line Items]
Total revenue	3,693	1,876	6,513	3,830
Transferred over Time | Identity verification services and other
Disaggregation of Revenue [Line Items]
Total revenue	$ 5,705	$ 3,628	$ 10,573	$ 6,604