Revenues - Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2017
Disaggregation of revenue
Revenue	$ 1,034,531	$ 987,170
U.S. dollar
Disaggregation of revenue
Revenue	936,062	889,477
British Pound Sterling
Disaggregation of revenue
Revenue	65,152	63,121
Euro
Disaggregation of revenue
Revenue	25,611	26,597
Other
Disaggregation of revenue
Revenue	7,706	7,975
Volume-based revenues
Disaggregation of revenue
Revenue	771,719	727,940
Non-volume related revenues
Disaggregation of revenue
Revenue	262,812	259,230
Issuer Solutions
Disaggregation of revenue
Revenue	470,159	457,359
Issuer Solutions | U.S. dollar
Disaggregation of revenue
Revenue	372,000	359,870
Issuer Solutions | British Pound Sterling
Disaggregation of revenue
Revenue	65,152	63,121
Issuer Solutions | Euro
Disaggregation of revenue
Revenue	25,611	26,597
Issuer Solutions | Other
Disaggregation of revenue
Revenue	7,396	7,771
Issuer Solutions | Volume-based revenues
Disaggregation of revenue
Revenue	230,211	219,271
Issuer Solutions | Non-volume related revenues
Disaggregation of revenue
Revenue	239,948	238,088
Merchant Solutions
Disaggregation of revenue
Revenue	345,181	319,423
Merchant Solutions | U.S. dollar
Disaggregation of revenue
Revenue	344,871	319,219
Merchant Solutions | Other
Disaggregation of revenue
Revenue	310	204
Merchant Solutions | Volume-based revenues
Disaggregation of revenue
Revenue	322,812	298,948
Merchant Solutions | Non-volume related revenues
Disaggregation of revenue
Revenue	22,369	20,475
Consumer Solutions
Disaggregation of revenue
Revenue	219,191	210,388
Consumer Solutions | U.S. dollar
Disaggregation of revenue
Revenue	219,191	210,388
Consumer Solutions | Volume-based revenues
Disaggregation of revenue
Revenue	218,696	209,721
Consumer Solutions | Non-volume related revenues
Disaggregation of revenue
Revenue	$ 495	$ 667