Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Fair Value - Visa Derivative (Details) - Funding Swap (Visa Derivative) $ in Millions	Sep. 30, 2018 USD ($)	Jun. 28, 2018	Dec. 31, 2017 USD ($)	Dec. 31, 2016
Class B restricted shares
Fair value
Conversion rate		1.6298		1.6483
Fair Value Measurements, Recurring \| Level 3
Fair value
Derivative Liability	$ 3.4		$ 5.4