Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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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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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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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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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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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 cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

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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, Repurchase Percentage

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

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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		12 Months Ended
	Apr. 07, 2020	Apr. 07, 2016	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Feb. 10, 2020
Debt Instrument [Line Items]
Long-term debt			$ 2,855,164,000		$ 2,972,674,000
Letters of credit			51,300,000		51,314,000
Borrowings on revolving credit facility			0	$ 863,756,000
Remaining borrowing capacity on revolving credit facility			768,700,000		768,686,000
Participation debt
Debt Instrument [Line Items]
Long-term debt			$ 0		$ 50,000,000
Average interest rate			3.38%		4.17%
Participation debt \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Margin on variable rate, percent			2.25%
2016 Credit Agreement
Debt Instrument [Line Items]
Letters of credit			$ 2,400,000,000
Average interest rate			3.10%		4.00%
Australian Securitization Facility
Debt Instrument [Line Items]
Percentage used as collateral			85.00%
Interest rate during period, percent			1.76%		1.80%
Short-term debt, net			$ 66,400,000		$ 78,600,000
European Securitization Facility
Debt Instrument [Line Items]
Interest rate during period, percent			0.91%		0.63%
Debt instrument, term		5 years
Securitized debt			$ 21,800,000		$ 25,700,000
Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Debt Instrument [Line Items]
Incremental revolving commitments						$ 1,400,000,000
Current borrowing capacity					820,000,000.0
Line of Credit
Debt Instrument [Line Items]
Long-term debt			$ 0		$ 35,000,000.0
Average interest rate			1.68%		2.36%
Credit Facility Term Loans \| Tranche B term loan \| Base Rate
Debt Instrument [Line Items]
Margin on variable rate, percent			1.25%
Credit Facility Term Loans \| Tranche B term loan \| Eurocurrency Rate
Debt Instrument [Line Items]
Margin on variable rate, percent			2.25%
WEX Latin America debt
Debt Instrument [Line Items]
Long-term debt			$ 2,385,000		$ 2,660,000
Interest rate during period, percent			29.04%		35.04%
WEX Latin America debt			$ 2,400,000		$ 2,700,000
Secured debt
Debt Instrument [Line Items]
Long-term debt			88,176,000		104,261,000
Secured debt \| Line of Credit \| 2016 Credit Agreement
Debt Instrument [Line Items]
Long-term debt			2,364,603,000		2,380,755,000
Secured debt \| Line of Credit \| Tranche A term loan
Debt Instrument [Line Items]
Long-term debt			911,225,000		923,707,000
Secured debt \| Line of Credit \| Tranche B term loan
Debt Instrument [Line Items]
Long-term debt			1,453,378,000		1,457,048,000
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 \| Senior Notes, 4.75 Percent
Debt Instrument [Line Items]
Redemption price, percent					100.792%
Repurchase price, percent					101.00%
Senior Notes \| Notes payable
Debt Instrument [Line Items]
Long-term debt			400,000,000		$ 400,000,000
Senior notes			$ 400,000,000.0
Interest rate, stated percentage			4.75%
Line of Credit
Debt Instrument [Line Items]
Remaining borrowing capacity on revolving credit facility			$ 380,000,000.0		$ 355,000,000.0
Subsequent Event \| Revolving line-of-credit facility under 2016 Credit Agreement
Debt Instrument [Line Items]
Current borrowing capacity	$ 618,700,000
Borrowings on revolving credit facility	$ 150,000,000.0