v2.4.1.9

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2012	Aug. 30, 2012	Jan. 30, 2013
Significant Accounting Policies [Line Items]
Goodwill impairment loss	$ 0us-gaap_GoodwillImpairmentLoss	$ 0us-gaap_GoodwillImpairmentLoss	$ 17,508,000us-gaap_GoodwillImpairmentLoss
Impairment expense			8,903,000us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf
Impairment of other long lived assets			600,000us-gaap_OtherAssetImpairmentCharges
Offset of waived finance fees	6,002,000wex_OffsetOfWaivedFinanceFees	4,557,000wex_OffsetOfWaivedFinanceFees	3,905,000wex_OffsetOfWaivedFinanceFees
Unik Financial Services
Significant Accounting Policies [Line Items]
Other debt		7,278,000us-gaap_OtherLongTermDebt / us-gaap_BusinessAcquisitionAxis = wex_UnikSAMember
Percent of ownership interest acquired	51.00%us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired / us-gaap_BusinessAcquisitionAxis = wex_UnikSAMember						51.00%us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired / us-gaap_BusinessAcquisitionAxis = wex_UnikSAMember
Wright Express Prepaid Australia
Significant Accounting Policies [Line Items]
Goodwill impairment loss				16,171,000us-gaap_GoodwillImpairmentLoss / us-gaap_BusinessAcquisitionAxis = wex_WrightExpressPrepaidAustraliaMember
Financial Automation Limited
Significant Accounting Policies [Line Items]
Goodwill impairment loss					1,337,000us-gaap_GoodwillImpairmentLoss / us-gaap_BusinessAcquisitionAxis = wex_FinancialAutomationLimitedMember	1,337,000us-gaap_GoodwillImpairmentLoss / us-gaap_BusinessAcquisitionAxis = wex_FinancialAutomationLimitedMember
Senior Notes
Significant Accounting Policies [Line Items]
Debt instrument, aggregate principal amount	$ 400,000,000us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = us-gaap_SeniorNotesMember
Debt instrument, stated rate	4.75%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = us-gaap_SeniorNotesMember							4.75%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = us-gaap_SeniorNotesMember

X

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

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X

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

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X

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Subparagraph (SX 210.5-02.22(a)(1))

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- Definition

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The aggregate amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

The charge against earnings resulting from the write down of long lived assets other than goodwill due to the difference between the carrying value and lower fair value.

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Balance Type:	debit
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X

- Definition

Including both current and noncurrent portions, carrying amount as of the balance sheet date of other forms of debt not elsewhere specified in the taxonomy with initial maturities beyond one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Subparagraph (SX 210.5-02.22)

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Offset of waived finance fees.

+ References

No definition available.

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Balance Type:
Period Type:

X

- Details

Name:	us-gaap_BusinessAcquisitionAxis=wex_UnikSAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_BusinessAcquisitionAxis=wex_WrightExpressPrepaidAustraliaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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Period Type: