Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Carrying Amount of Goodwill Allocated by Domestic and Foreign Operations

The carrying amount of goodwill at June 30, 2022 and December 31, 2021 allocated by domestic and foreign operations is as follows (in millions):

	Brokerage		Risk Management		Corporate		Total
At June 30, 2022
United States	$	4,917.6	$	64.8	$	—	$	4,982.4
United Kingdom		1,978.1		19.5		—		1,997.6
Canada		592.2		—		—		592.2
Australia		456.6		10.5		—		467.1
New Zealand		203.5		9.5		—		213.0
Other foreign		763.8		—		20.3		784.1
Total goodwill	$	8,911.8	$	104.3	$	20.3	$	9,036.4
At December 31, 2021
United States	$	4,409.1	$	64.8	$	—	$	4,473.9
United Kingdom		2,198.7		15.0		—		2,213.7
Canada		572.9		—		—		572.9
Australia		487.2		10.9		—		498.1
New Zealand		217.6		10.2		—		227.8
Other foreign		659.1		—		20.7		679.8
Total goodwill	$	8,544.6	$	100.9	$	20.7	$	8,666.2

Changes in Carrying Amount of Goodwill

The changes in the carrying amount of goodwill for the six-month period ended June 30, 2022 are as follows (in millions):

	Brokerage			Risk Management			Corporate			Total
Balance as of December 31, 2021	$	8,544.6		$	100.9		$	20.7		$	8,666.2
Goodwill acquired during the period		207.6			6.0			—			213.6
Goodwill true-ups due to appraisals and other acquisition    adjustments (see Note 3)		407.8			—			0.2			408.0
Foreign currency translation adjustments during the period		(248.2	)		(2.6	)		(0.6	)		(251.4	)
Balance as of June 30, 2022	$	8,911.8		$	104.3		$	20.3		$	9,036.4

Major Classes of Amortizable Intangible Assets

Major classes of amortizable intangible assets at June 30, 2022 and December 31, 2021 consist of the following (in millions):

	June 30,			December 31,
	2022			2021
Expiration lists	$	6,091.6		$	6,696.8
Accumulated amortization - expiration lists		(2,973.4	)		(2,812.2	)
		3,118.2			3,884.6
Non-compete agreements		83.0			76.0
Accumulated amortization - non-compete agreements		(64.4	)		(62.8	)
		18.6			13.2
Trade names		104.9			105.2
Accumulated amortization - trade names		(50.8	)		(49.0	)
		54.1			56.2
Net amortizable assets	$	3,190.9		$	3,954.0

Estimated Aggregate Amortization Expense

Estimated aggregate amortization expense for each of the next five years and thereafter is as follows (in millions):

2022 (remaining six months)	$	223.9
2023		429.3
2024		392.4
2025		350.5
2026		312.1
Thereafter		1,482.7
Total	$	3,190.9