Employee Benefits (Tables)

9 Months Ended

Sep. 30, 2016

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
	2016			2015			2016			2015			2016			2015
Service cost	$	—		$	—		$	—		$	—		$	—		$	—
Interest cost	37			50			28			33			7			8
Expected return on plan assets, net of administration expenses	(58		)	(77		)	(39		)	(38		)	(12		)	(12		)
Amortization of prior-service cost	—			—			1			—			—			—
Amortization of net actuarial loss	7			11			12			14			3			2
Net periodic (benefit) cost	(14		)	(16		)	2			9			(2		)	(2		)
Loss on pension settlement	—			—			—			—			—			—
Curtailment gain and other	—			—			—			—			—			—
Total net periodic cost (benefit)	$	(14	)	$	(16	)	$	2		$	9		$	(2	)	$	(2	)
	Nine months ended September 30,
	U.K.						U.S.						Other
	2016			2015			2016			2015			2016			2015
Service cost	$	—		$	—		$	—		$	2		$	—		$	—
Interest cost	123			149			83			99			21			25
Expected return on plan assets, net of administration expenses	(187		)	(229		)	(117		)	(115		)	(36		)	(37		)
Amortization of prior-service cost	1			—			2			—			—			—
Amortization of net actuarial loss	24			31			37			41			8			8
Net periodic (benefit) cost	(39		)	(49		)	5			27			(7		)	(4		)
Loss on pension settlement	61			—			—			—			—			—
Curtailment gain and other	—			—			—			(1		)	—			—
Total net periodic cost (benefit)	$	22		$	(49	)	$	5		$	26		$	(7	)	$	(4	)