Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 149,738	$ 116,976
Intangible assets, accumulated amortization	(84,159)	(74,914)
Intangible assets, net	65,579	42,062
Merchant portfolios
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	77,998	46,716
Intangible assets, accumulated amortization	(44,888)	(41,915)
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	3,390	3,390
Intangible assets, accumulated amortization	(3,390)	(3,243)
Tradename
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	2,870	2,580
Intangible assets, accumulated amortization	(953)	(776)
Acquired technology
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	14,390	13,200
Intangible assets, accumulated amortization	(9,642)	(7,928)
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	51,090	51,090
Intangible assets, accumulated amortization	$ (25,286)	$ (21,052)