Employee Benefits (Tables)

6 Months Ended

Jun. 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 June 30,
	U.K. and Non-U.S.						U.S.
	2013			2012			2013			2012
Service cost	$	4		$	4		$	—		$	—
Interest cost	62			66			28			30
Expected return on plan assets	(88		)	(81		)	(35		)	(32		)
Amortization of net actuarial loss	19			15			13			11
Net periodic benefit cost	$	(3	)	$	4		$	6		$	9

	Six months ended June 30,
	U.K. and Non-U.S.						U.S.
	2013			2012			2013			2012
Service cost	$	9		$	8		$	—		$	—
Interest cost	126			132			56			60
Expected return on plan assets	(178		)	(161		)	(69		)	(64		)
Amortization of net actuarial loss	37			29			26			22
Net periodic benefit cost	$	(6	)	$	8		$	13		$	18