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

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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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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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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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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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Debt Covenant, One Time Consideration Payment, Minimum

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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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Securitization Facility

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Financing and Other Debt - Additional Information (Details) - USD ($)				1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Aug. 24, 2018	Jan. 17, 2018	Apr. 07, 2016	Jan. 31, 2018	Mar. 31, 2018	Sep. 30, 2018	Dec. 31, 2017	Aug. 23, 2018	Jan. 16, 2018
Debt Instrument [Line Items]
Loss on extinguishment of debt					$ 1,100,000
General and administrative costs incurred				$ 3,800,000
Debt issuance costs				$ 6,100,000
Long-term debt						$ 2,414,233,000	$ 2,461,048,000
Eurocurrency Rate
Debt Instrument [Line Items]
Interest rate during period, percent		2.25%
Base Rate
Debt Instrument [Line Items]
Interest rate during period, percent		1.25%
2016 Credit Agreement Tranche A \| Interest Rate Option One \| Eurocurrency Rate
Debt Instrument [Line Items]
Margin on variable rate, percent						2.00%
Basis spread on variable rate, reduction in basis points		0.50%
2016 Credit Agreement Tranche B
Debt Instrument [Line Items]
Weighted average annual interest rate, percent						4.30%	4.20%
2016 Credit Agreement Tranche B \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate, reduction in basis points	0.25%
2016 Credit Agreement Tranche B \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate, reduction in basis points	0.25%
2016 Credit Agreement Tranche B \| Interest Rate Option One \| Eurocurrency Rate
Debt Instrument [Line Items]
Margin on variable rate, percent						2.25%
Debt instrument, interest rate, floor						0.00%
2016 Credit Agreement
Debt Instrument [Line Items]
Debt covenant, one time consideration payment, minimum	$ 300,000,000
Australian Securitization Facility
Debt Instrument [Line Items]
Interest rate during period, percent						2.79%	2.53%
Debt instrument, term						1 year
Percentage used as collateral						85.00%
Short-term debt, net						$ 87,900,000	$ 90,000,000
European Securitization Facility
Debt Instrument [Line Items]
Interest rate during period, percent						0.91%	1.11%
Debt instrument, term			5 years
Securitized debt						$ 23,700,000	$ 17,900,000
Loan Participations and Assignments
Debt Instrument [Line Items]
Long-term debt						140,965,000	184,990,000
Debt balance						$ 141,000,000	$ 185,000,000
Loan Participations and Assignments \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Margin on variable rate, percent						2.25%
Loan Participations and Assignments, Amounts Maturing August 2018
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount						$ 75,400,000
Loan Participations and Assignments, Amounts Maturing August 2020
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount						50,000,000
Loan Participations and Assignments, Amounts Maturing On Demand
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount						15,600,000.0
Credit Facility Term Loans \| 2016 Credit Agreement Tranche A
Debt Instrument [Line Items]
Current borrowing capacity						455,000,000
Mandatory quarterly payments						5,400,000
Credit Facility Term Loans \| 2016 Credit Agreement Tranche B
Debt Instrument [Line Items]
Current borrowing capacity		$ 1,335,000,000				1,335,000,000			$ 1,182,000,000
Mandatory quarterly payments						3,400,000
Credit Facility Term Loans \| 2016 Credit Agreement
Debt Instrument [Line Items]
Current borrowing capacity	25,000,000
Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Debt Instrument [Line Items]
Current borrowing capacity	$ 720,000,000					$ 720,000,000		$ 570,000,000
Debt covenant, consolidated leverage ratio, period one	5.00
Debt covenant, consolidated leverage ratio, period two	4.50
Debt covenant, consolidated leverage ratio, period three	4.00
Debt covenant, interim consolidated leverage ratio	4.25
Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement \| Base Rate
Debt Instrument [Line Items]
Interest rate during period, percent	1.00%
Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate during period, percent	2.00%
WEX Latin America
Debt Instrument [Line Items]
Weighted average annual interest rate, percent						16.87%	21.20%
Long-term debt						$ 7,808,000	$ 9,747,000
Senior Notes \| Notes payable
Debt Instrument [Line Items]
Long-term debt						$ 400,000,000	400,000,000
Interest rate, stated percentage						4.75%
Line of Credit
Debt Instrument [Line Items]
Long-term debt						$ 0	$ 0
Maximum borrowing capacity						$ 310,000,000