Employee Benefits (Tables)

6 Months Ended

Jun. 30, 2021

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 for Aon’s significant U.K., U.S., and other major pension plans, which are located in the Netherlands and Canada. Service cost is reported in Compensation and benefits and all other components are reported in Other income (expense) as follows (in millions):

	Three Months Ended June 30,
	U.K.				U.S.				Other
	2021		2020		2021		2020		2021		2020
Service cost	$	—	$	—	$	—	$	—	$	—	$	—
Interest cost	17		21		14		21		3		5
Expected return on plan assets, net of administration expenses	(35)		(39)		(32)		(33)		(8)		(9)
Amortization of prior-service cost	1		1		—		—		—		—
Amortization of net actuarial loss	8		8		20		17		3		3
Net periodic (benefit) cost	(9)		(9)		2		5		(2)		(1)
Loss on pension settlement	—		2		—		—		—		—
Total net periodic (benefit) cost	$	(9)	$	(7)	$	2	$	5	$	(2)	$	(1)
	Six Months Ended June 30,
	U.K.				U.S.				Other
	2021		2020		2021		2020		2021		2020
Service cost	$	—	$	—	$	—	$	—	$	—	$	—
Interest cost	33		43		28		42		6		9
Expected return on plan assets, net of administration expenses	(69)		(78)		(64)		(66)		(16)		(17)
Amortization of prior-service cost	2		1		—		—		—		—
Amortization of net actuarial loss	16		15		39		34		7		6
Net periodic (benefit) cost	(18)		(19)		3		10		(3)		(2)
Loss on pension settlement	—		2		—		—		—		—
Total net periodic (benefit) cost	$	(18)	$	(17)	$	3	$	10	$	(3)	$	(2)

Schedule of Employer's Contributions

The following table summarizes contributions made to the Company’s significant pension plans (in millions):

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Contributions to U.K. pension plans	$	2	$	2	$	6	$	4
Contributions to U.S. pension plans	8		7		46		38
Contributions to other major pension plans	2		9		10		11
Total contributions	$	12	$	18	$	62	$	53