Employee Benefits (Tables)

6 Months Ended

Jun. 30, 2017

Retirement Benefits [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
	2017			2016			2017			2016			2017			2016
Service cost	$	—		$	—		$	—		$	—		$	—		$	—
Interest cost	30			43			24			28			6			7
Expected return on plan assets, net of administration expenses	(49		)	(65		)	(35		)	(39		)	(11		)	(12		)
Amortization of prior-service cost	—			1			1			1			—			—
Amortization of net actuarial loss	8			9			12			12			3			3
Net periodic cost (benefit)	$	(11	)	$	(12	)	$	2		$	2		$	(2	)	$	(2	)
Loss on pension settlement	—			61			—			—			—			—
Total net periodic cost (benefit)	$	(11	)	$	49		$	2		$	2		$	(2	)	$	(2	)
	Six months ended June 30
	U.K.						U.S.						Other
	2017			2016			2017			2016			2017			2016
Service cost	$	—		$	—		$	—		$	—		$	—		$	—
Interest cost	60			86			48			55			12			14
Expected return on plan assets, net of administration expenses	(97		)	(129		)	(70		)	(78		)	(22		)	(24		)
Amortization of prior-service cost	—			1			1			1			—			—
Amortization of net actuarial loss	15			17			25			25			6			5
Net periodic cost (benefit)	$	(22	)	$	(25	)	$	4		$	3		$	(4	)	$	(5	)
Loss on pension settlement	—			61			—			—			—			—
Total net periodic cost (benefit)	$	(22	)	$	36		$	4		$	3		$	(4	)	$	(5	)