Employee Benefits (Tables)

3 Months Ended

Mar. 31, 2015

Compensation and Retirement Disclosure [Abstract]

Components of net periodic benefit cost for the pension plans

The following table provides the components of the net periodic benefit cost recognized in the Condensed Consolidated Statements of Income in Compensation and benefits for Aon's material U.K., U.S., and other significant international pension plans located in the Netherlands and Canada (in millions):

	Three months ended March 31,
	U.K.						U.S.						Other
	2015			2014			2015			2014			2015			2014
Service cost	$	—		$	—		$	1		$	—		$	—		$	—
Interest cost	49			58			33			32			8			12
Expected return on plan assets	(75		)	(82		)	(39		)	(39		)	(12		)	(15		)
Amortization of net actuarial loss	10			13			14			10			3			2
Net periodic (benefit) cost	(16		)	(11		)	9			3			(1		)	(1		)
Curtailment loss (gain) and other	—			—			(1		)	1			—			(3		)
Total net periodic (benefit) cost	$	(16	)	$	(11	)	$	8		$	4		$	(1	)	$	(4	)