Off-Balance Sheet Arrangements (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
Dec. 31, 2025 |
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||||
| HSA assets amount serving as custodian | $ 5,400.0 | $ 5,400.0 | |||
| HSA assets deposited and managed by third party depository partners | 613.5 | 613.5 | |||
| HSA deposits | 4,758.0 | 4,758.0 | $ 4,200.0 | ||
| WEX Europe Services And WEX Bank | |||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||||
| Gain (loss) on sale of factoring receivables | 2.4 | $ 2.5 | $ 5.0 | $ 6.6 | |
| WEX Europe Services | |||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||||
| Agreement termination minimum notification period | 90 days | ||||
| Proceeds from sale of factoring receivables | 93.3 | 127.2 | $ 273.7 | 360.0 | |
| WEX Bank | |||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||||
| Proceeds from sale of factoring receivables | $ 5,200.0 | $ 4,500.0 | $ 9,100.0 | $ 10,400.0 | |
| Termination notice period | 30 days | ||||