Employee Benefits (Tables)

9 Months Ended

Sep. 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 September 30,
	U.K.						U.S.						Other
	2015			2014			2015			2014			2015			2014
Service cost	$	—		$	—		$	—		$	—		$	—		$	—
Interest cost	50			58			33			32			8			12
Expected return on plan assets	(77		)	(82		)	(38		)	(39		)	(12		)	(15		)
Amortization of net actuarial loss	11			13			14			11			2			2
Net periodic (benefit) cost	(16		)	(11		)	9			4			(2		)	(1		)
Curtailment loss (gain) and other	—			—			—			—			—			—
Total net periodic (benefit) cost	$	(16	)	$	(11	)	$	9		$	4		$	(2	)	$	(1	)

	Nine months ended September 30,
	U.K.						U.S.						Other
	2015			2014			2015			2014			2015			2014
Service cost	$	—		$	—		$	2		$	—		$	—		$	—
Interest cost	149			174			99			96			25			36
Expected return on plan assets	(229		)	(247		)	(115		)	(117		)	(37		)	(45		)
Amortization of net actuarial loss	31			40			41			32			8			6
Net periodic (benefit) cost	(49		)	(33		)	27			11			(4		)	(3		)
Curtailment (gain) loss and other	—			—			(1		)	1			—			(3		)
Total net periodic (benefit) cost	$	(49	)	$	(33	)	$	26		$	12		$	(4	)	$	(6	)