Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2020

Goodwill And Intangible Assets Disclosure [Abstract]

Carrying Amount of Goodwill Allocated by Domestic and Foreign Operations

The carrying amount of goodwill at December 31, 2020 and 2019 allocated by domestic and foreign operations is as follows (in millions):

	Brokerage		Risk Management		Corporate		Total
At December 31, 2020
United States	$	3,399.8	$	33.2	$	-	$	3,433.0
United Kingdom		1,328.3		15.1		-		1,343.4
Canada		492.9		-		-		492.9
Australia		462.1		11.5		-		473.6
New Zealand		221.9		10.7		-		232.6
Other foreign		148.6		-		2.9		151.5
Total goodwill - net	$	6,053.6	$	70.5	$	2.9	$	6,127.0
At December 31, 2019
United States		3,163.8		33.1		-		3,196.9
United Kingdom		1,177.8		12.9		-		1,190.7
Canada		454.4		-		-		454.4
Australia		416.5		10.5		-		427.0
New Zealand		208.0		10.1		-		218.1
Other foreign		128.4		-		3.0		131.4
Total goodwill - net	$	5,548.9	$	66.6	$	3.0	$	5,618.5

Changes in Carrying Amount of Goodwill

The changes in the carrying amount of goodwill for 2020 and 2019 are as follows (in millions):

	Brokerage			Risk Management			Corporate			Total
Balance as of December 31, 2018	$	4,573.6		$	49.3		$	2.7		$	4,625.6
Goodwill acquired during the year		958.4			16.9			0.4			975.7
Goodwill adjustments related to appraisals and other acquisition    adjustments		0.2			(0.2	)		-			-
Goodwill written-off related to sales of business		(7.2	)		-			-			(7.2	)
Foreign currency translation adjustments during the year		23.9			0.6			(0.1	)		24.4
Balance as of December 31, 2019		5,548.9			66.6			3.0			5,618.5
Goodwill acquired during the year		359.6			-			-			359.6
Goodwill adjustments related to appraisals and other acquisition    adjustments		29.8			1.7			-			31.5
Foreign currency translation adjustments during the year		115.3			2.2			(0.1	)		117.4
Balance as of December 31, 2020	$	6,053.6		$	70.5		$	2.9		$	6,127.0

Major Classes of Amortizable Intangible Assets

Major classes of amortizable intangible assets consist of the following (in millions):

	December 31,
	2020			2019
Expiration lists	$	4,753.2		$	4,246.0
Accumulated amortization - expiration lists		(2,436.7	)		(2,004.3	)
		2,316.5			2,241.7
Non-compete agreements		75.9			68.4
Accumulated amortization - non-compete agreements		(57.8	)		(52.5	)
		18.1			15.9
Trade names		107.8			91.8
Accumulated amortization - trade names		(42.5	)		(30.7	)
		65.3			61.1
Net amortizable assets	$	2,399.9		$	2,318.7

Estimated Aggregate Amortization Expense

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

2021	$	378.4
2022		352.3
2023		327.1
2024		291.3
2025		251.3
Thereafter		799.5
Total	$	2,399.9