Contract Acquisition Costs, Net - Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Conversion
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amortization expense related to contract acquisition costs	$ 29,625	$ 28,811	$ 27,392
Processing rights
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amortization expense related to contract acquisition costs	$ 21,357	$ 19,804	$ 17,039

Amount of amortization of other deferred costs recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration