Equipment and Improvements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Equipment and Improvements
Equipment and improvements, Gross	$ 215,716		$ 215,716		$ 197,108
Less accumulated depreciation	(118,336)		(118,336)		(106,889)
Foreign currency translation adjustment	2,977		2,977		6,368
Total	100,357		100,357		96,587
Depreciation
Depreciation expense	9,500	$ 7,200	18,500	$ 14,300
Decrease in equipment and improvements			7,500	2,700
Decrease in accumulated depreciation			7,100	$ 2,600
Card Processing
Equipment and Improvements
Equipment and improvements, Gross	113,489		113,489		102,789
Office equipment
Equipment and Improvements
Equipment and improvements, Gross	42,007		42,007		37,476
Computer software
Equipment and Improvements
Equipment and improvements, Gross	41,278		$ 41,278		$ 38,669
Estimated useful lives			3 years		3 years
Leasehold improvements
Equipment and Improvements
Equipment and improvements, Gross	13,120		$ 13,120		$ 12,764
Furniture and fixtures
Equipment and Improvements
Equipment and improvements, Gross	$ 5,822		$ 5,822		$ 5,410
Minimum | Card Processing
Equipment and Improvements
Estimated useful lives			3 years		3 years
Minimum | Office equipment
Equipment and Improvements
Estimated useful lives			3 years		3 years
Minimum | Furniture and fixtures
Equipment and Improvements
Estimated useful lives			5 years		5 years
Maximum | Card Processing
Equipment and Improvements
Estimated useful lives			5 years		5 years
Maximum | Office equipment
Equipment and Improvements
Estimated useful lives			5 years		5 years
Maximum | Furniture and fixtures
Equipment and Improvements
Estimated useful lives			7 years		7 years