Segments (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019		Mar. 31, 2020	Mar. 31, 2019		Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenue	$ 39,178	$ 85,394		$ 80,289	$ 170,262
Operating expenses
Interchange and network fees	0	54,685	[1]	0	110,514	[1]
Other costs (benefits) of services	11,955	10,193		24,873	19,983
Selling general and administrative	20,786	14,319		40,073	26,835
Depreciation and amortization	4,538	3,898		9,193	7,450
Change in fair value of contingent consideration	(142)	2,502		12	2,153
Income (loss) from operations	2,041	(203)		6,138	3,327
Processing margin	32,393	24,259		65,890	47,347
Assets	351,182	218,499		351,182	218,499		$ 349,302
Goodwill	167,054	104,651		167,054	104,651		168,284
Merchant Services
Segment Reporting Information [Line Items]
Revenue	25,018	76,875		52,483	154,577
Operating expenses
Interchange and network fees		53,121			107,485
Other costs (benefits) of services	11,297	9,725		23,410	19,121
Selling general and administrative	6,469	6,226		12,791	12,317
Depreciation and amortization	2,861	2,917		5,808	5,699
Change in fair value of contingent consideration	(400)	(390)		(1,606)	(709)
Income (loss) from operations	4,791	5,276		12,080	10,664
Processing margin	19,245	17,584		40,141	35,211
Assets	200,159	152,851		200,159	152,851
Goodwill	107,539	71,950		107,539	71,950		108,472
Residual expense	5,524	3,555		11,068	7,240
Proprietary Software and Payments
Segment Reporting Information [Line Items]
Revenue	14,691	8,519		28,747	15,685
Operating expenses
Interchange and network fees		1,564			3,029
Other costs (benefits) of services	1,188	468		2,403	862
Selling general and administrative	7,717	3,675		15,653	6,662
Depreciation and amortization	1,498	842		3,037	1,503
Change in fair value of contingent consideration	258	2,892		1,618	2,862
Income (loss) from operations	4,030	(922)		6,036	767
Processing margin	13,675	6,675		26,684	12,136
Assets	109,689	59,077		109,689	59,077
Goodwill	59,515	32,701		59,515	32,701		59,812
Residual expense	172	188		340	342
Other
Segment Reporting Information [Line Items]
Revenue	(531)	0		(941)	0
Operating expenses
Interchange and network fees		0			0
Other costs (benefits) of services	(530)	0		(940)	0
Selling general and administrative	6,600	4,418		11,629	7,856
Depreciation and amortization	179	139		348	248
Change in fair value of contingent consideration	0	0		0	0
Income (loss) from operations	(6,780)	(4,557)		(11,978)	(8,104)
Processing margin	(527)	0		(935)	0
Assets	41,334	6,571		41,334	6,571
Goodwill	0	0		0	0		$ 0
Residual expense	$ (526)	$ 0		$ (934)	$ 0

[1] Effective October 1, 2019, the Company's revenues are presented net of interchange and network fees in accordance with Accounting Standards Codification Topic 606, Revenue from Contracts with Customers. See Note 2 to our condensed consolidated financial statements for a description of the recently adopted accounting pronouncement.