Employee Benefits (Tables)

6 Months Ended

Jun. 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 June 30,
	U.K.						U.S.						Other
	2016			2015			2016			2015			2016			2015
Service cost	$	—		$	—		$	—		$	1		$	—		$	—
Interest cost	43			50			28			33			7			9
Expected return on plan assets, net of administration expenses	(65		)	(77		)	(39		)	(38		)	(12		)	(13		)
Amortization of prior-service cost	1			—			1			—			—			—
Amortization of net actuarial loss	9			10			12			13			3			3
Net periodic (benefit) cost	(12		)	(17		)	2			9			(2		)	(1		)
Loss on pension settlement	61			—			—			—			—			—
Curtailment gain and other	—			—			—			—			—			—
Total net periodic cost (benefit)	$	49		$	(17	)	$	2		$	9		$	(2	)	$	(1	)
	Six months ended June 30,
	U.K.						U.S.						Other
	2016			2015			2016			2015			2016			2015
Service cost	$	—		$	—		$	—		$	2		$	—		$	—
Interest cost	86			99			55			66			14			17
Expected return on plan assets, net of administration expenses	(129		)	(152		)	(78		)	(77		)	(24		)	(25		)
Amortization of prior-service cost	1			—			1			—			—			—
Amortization of net actuarial loss	17			20			25			27			5			6
Net periodic (benefit) cost	(25		)	(33		)	3			18			(5		)	(2		)
Loss on pension settlement	61			—			—			—			—			—
Curtailment gain and other	—			—			—			(1		)	—			—
Total net periodic cost (benefit)	$	36		$	(33	)	$	3		$	17		$	(5	)	$	(2	)