Income Taxes - Components Of Income Tax Expense (Benefit) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Current, United States	$ 43,565us-gaap_CurrentFederalTaxExpenseBenefit	$ 52,118us-gaap_CurrentFederalTaxExpenseBenefit	$ 48,632us-gaap_CurrentFederalTaxExpenseBenefit
Deferred, United States	51,581	31,020	22,560
Current, State and Local	3,326	5,176	3,460
Deferred, State and Local	3,979	1,562	(1,301)
Current, Foreign	8,009us-gaap_CurrentForeignTaxExpenseBenefit	5,255us-gaap_CurrentForeignTaxExpenseBenefit	18,681us-gaap_CurrentForeignTaxExpenseBenefit
Deferred, Foreign	(8,839)	(5,029)	17,442
Current, Total	54,900us-gaap_CurrentIncomeTaxExpenseBenefit	62,549us-gaap_CurrentIncomeTaxExpenseBenefit	70,773us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred, Total	$ 46,721wex_DeferredIncomeTaxesExpenseBenefit	$ 27,553wex_DeferredIncomeTaxesExpenseBenefit	$ 38,701wex_DeferredIncomeTaxesExpenseBenefit

Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.

Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred federal income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred foreign income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations.