Reconciliation of Adjusted Net Income to Net Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting [Abstract]
Adjusted net income attributable to WEX Inc.	$ 41,612	$ 39,840
Unrealized gain (loss) on fuel price derivatives	2,823	(5,882)
Amortization of acquired intangible assets	(8,287)	(8,379)
Stock-based compensation	(2,423)	(2,406)
Deferred loan costs associated with the extinguishment of debt	0	(1,004)
ANI adjustments attributable to non-controlling interests	185	346
Tax impact	2,632	6,174
Net earnings attributable to WEX Inc.	$ 36,542	$ 28,689