Employee Benefits (Tables)

3 Months Ended

Mar. 31, 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 March 31,
	U.K. and Non-U.S.						U.S.
	2013			2012			2013			2012
Service cost	$	5		$	4		$	—		$	—
Interest cost	64			66			28			30
Expected return on plan assets	(90		)	(80		)	(34		)	(32		)
Amortization of net actuarial loss	18			14			13			11
Net periodic benefit cost	$	(3	)	$	4		$	7		$	9