Employee Benefits (Tables)

9 Months Ended

Sep. 30, 2013

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 for Aon’s U.S. pension plans, along with its most significant international pension plans, which are located in the U.K., the Netherlands and Canada (in millions):

	Three months ended September 30,
	U.K. and Non-U.S.						U.S.
	2013			2012			2013			2012
Service cost	$	5		$	4		$	—		$	—
Interest cost	63			66			28			29
Expected return on plan assets	(89		)	(80		)	(34		)	(31		)
Amortization of net actuarial loss	18			15			13			10
Net periodic (benefit) cost	$	(3	)	$	5		$	7		$	8

	Nine months ended September 30,
	U.K. and Non-U.S.						U.S.
	2013			2012			2013			2012
Service cost	$	14		$	12		$	—		$	—
Interest cost	189			198			84			89
Expected return on plan assets	(267		)	(241		)	(103		)	(95		)
Amortization of net actuarial loss	55			44			39			32
Net periodic (benefit) cost	$	(9	)	$	13		$	20		$	26