Financing and Other Debt - Summary of Outstanding Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Principal	$ 3,132,090	$ 2,972,674
Current portion of gross debt	170,556	256,529
Less: Unamortized debt issuance costs/debt discount	(17,826)	(7,998)
Short-term debt, net	152,730	248,531
Long-term portion of gross debt	2,961,534	2,716,145
Less: Unamortized debt issuance costs/debt discount	(87,421)	(29,632)
Long-term debt, net	2,874,113	2,686,513
Participation debt
Debt Instrument [Line Items]
Principal	0	50,000
Borrowed Federal Funds
Debt Instrument [Line Items]
Principal	20,000	34,998
Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Supplemental information under 2016 Credit Agreement:
Remaining borrowing capacity on revolving credit facility		870,000
Secured debt
Debt Instrument [Line Items]
Principal	85,945	104,261
Secured debt \| Line of Credit \| 2016 Credit Agreement
Debt Instrument [Line Items]
Principal	2,316,145	2,380,755
Secured debt \| Line of Credit \| Tranche A term loan
Debt Instrument [Line Items]
Principal	873,777	923,707
Secured debt \| Line of Credit \| Tranche B term loan
Debt Instrument [Line Items]
Principal	1,442,368	1,457,048
Senior Notes \| Notes payable
Debt Instrument [Line Items]
Principal	400,000	400,000
Convertible Debt
Debt Instrument [Line Items]
Principal		0
Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Supplemental information under 2016 Credit Agreement:
Remaining borrowing capacity on revolving credit facility	818,372	768,686
Letter of Credit \| Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Supplemental information under 2016 Credit Agreement:
Letters of credit		51,314
WEX Latin America debt
Debt Instrument [Line Items]
Principal	$ 0	$ 2,660

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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