Employee Benefits (Tables)

6 Months Ended

Jun. 30, 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 June 30,
	U.K.						U.S.						Other
	2015			2014			2015			2014			2015			2014
Service cost	$	—		$	—		$	1		$	—		$	—		$	—
Interest cost	50			58			33			32			9			12
Expected return on plan assets	(77		)	(83		)	(38		)	(39		)	(13		)	(15		)
Amortization of net actuarial loss	10			14			13			11			3			2
Net periodic (benefit) cost	(17		)	(11		)	9			4			(1		)	(1		)
Curtailment loss (gain) and other	—			—			—			—			—			—
Total net periodic (benefit) cost	$	(17	)	$	(11	)	$	9		$	4		$	(1	)	$	(1	)

	Six months ended June 30,
	U.K.						U.S.						Other
	2015			2014			2015			2014			2015			2014
Service cost	$	—		$	—		$	2		$	—		$	—		$	—
Interest cost	99			116			66			64			17			24
Expected return on plan assets	(152		)	(165		)	(77		)	(78		)	(25		)	(30		)
Amortization of net actuarial loss	20			27			27			21			6			4
Net periodic (benefit) cost	(33		)	(22		)	18			7			(2		)	(2		)
Curtailment loss (gain) and other	—			—			(1		)	1			—			(3		)
Total net periodic (benefit) cost	$	(33	)	$	(22	)	$	17		$	8		$	(2	)	$	(5	)