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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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The average effective interest rate during the reporting period.

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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average interest rate of debt outstanding.

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No definition available.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of the required periodic payments of both interest and principal.

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Carrying amount of collateralized debt obligations with maturities initially due after one year or beyond the operating cycle, if longer, excluding the current portion. Obligations include, but not limited to, mortgage loans, chattel loans, and other borrowings secured by assets.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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Debt Instrument, Securitization Facility, Percentage of Receivables Used as Collateral

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Gain (Loss) On Extinguishment Of Debt, General And Administrative Costs Incurred

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Line of Credit Facility, Maximum Borrowing Capacity, Additional Capacity

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Securitization Facility

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Financing and Other Debt - Additional Information (Details) - USD ($)				3 Months Ended	6 Months Ended	12 Months Ended
	May 17, 2019	Jan. 18, 2019	Apr. 07, 2016	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Mar. 05, 2019
Debt Instrument [Line Items]
Debt issuance costs	$ 11,000,000.0	$ 3,400,000
Long-term debt				$ 2,980,229,000	$ 2,980,229,000	$ 2,383,047,000
Amounts Available				$ 719,526,000	$ 719,526,000	$ 666,486,000
2016 Credit Agreement
Debt Instrument [Line Items]
Average interest rate				4.60%	4.60%	4.70%
Delayed Draw Commitment
Debt Instrument [Line Items]
Current borrowing capacity		275,000,000.0
Loan Participations and Assignments
Debt Instrument [Line Items]
Average interest rate				4.67%	4.67%	4.30%
Long-term debt				$ 57,499,000	$ 57,499,000	$ 114,849,000
Amounts Available				$ 180,000,000	$ 180,000,000	$ 180,000,000
Loan Participations and Assignments \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Margin on variable rate, percent					2.25%
Australian Securitization Facility
Debt Instrument [Line Items]
Percentage used as collateral				85.00%	85.00%
Interest rate during period, percent					2.87%	2.89%
Short-term debt, net				$ 79,900,000	$ 79,900,000	$ 87,000,000.0
European Securitization Facility
Debt Instrument [Line Items]
Interest rate during period, percent					1.06%	0.98%
Debt instrument, term			5 years
Securitized debt				25,200,000	$ 25,200,000	$ 18,000,000.0
Credit Facility Term Loans \| Tranche A term loan
Debt Instrument [Line Items]
Current borrowing capacity						480,000,000.0	$ 250,000,000.0
Incremental revolving commitments		300,000,000
Mandatory quarterly payments					12,500,000
Loss on extinguishment of debt				1,300,000
General and administrative costs incurred	4,200,000	5,300,000
Credit Facility Term Loans \| Tranche B term loan
Debt Instrument [Line Items]
Current borrowing capacity						1,335,000,000.0
Incremental revolving commitments	$ 150,000,000.0
Mandatory quarterly payments					$ 3,700,000
Credit Facility Term Loans \| Tranche B term loan \| Base Rate
Debt Instrument [Line Items]
Margin on variable rate, percent					2.25%
Credit Facility Term Loans \| Tranche B term loan \| Eurocurrency Rate
Debt Instrument [Line Items]
Margin on variable rate, percent					1.25%
Credit Facility Term Loans \| Revolving line-of-credit facility under 2016 Credit Agreement
Debt Instrument [Line Items]
Current borrowing capacity							$ 50,000,000.0
Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Debt Instrument [Line Items]
Current borrowing capacity						720,000,000.0
Incremental revolving commitments		$ 25,000,000.0
Line of Credit
Debt Instrument [Line Items]
Long-term debt						$ 0
WEX Latin America
Debt Instrument [Line Items]
Interest rate during period, percent					24.35%	23.59%
WEX Latin America debt				4,554,000	$ 4,554,000	$ 16,242,000
Letter of Credit \| Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Debt Instrument [Line Items]
Current borrowing capacity						250,000,000.0
Swingline Loan \| Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Debt Instrument [Line Items]
Current borrowing capacity						20,000,000.0
Senior Notes \| Notes payable
Debt Instrument [Line Items]
Senior notes				$ 400,000,000.0	$ 400,000,000.0	$ 400,000,000.0
Interest rate, stated percentage				4.75%	4.75%	4.75%
Long-term debt				$ 400,000,000	$ 400,000,000	$ 400,000,000
Line of Credit
Debt Instrument [Line Items]
Amounts Available				$ 334,000,000.0	$ 334,000,000.0	$ 309,000,000.0