Goodwill and Other Intangible Assets

12 Months Ended

Dec. 31, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND OTHER INTANGIBLE ASSETS

The following table summarizes the carrying amount of goodwill and changes in the carrying amount of goodwill, by segment:


(in millions)	Environmental Solutions		Safety & Security Systems		Total
Balance at December 31, 2018	$	263.2	$	111.9	$	375.1
Acquisitions	13.9		—		13.9
Translation adjustments	0.2		(0.4)		(0.2)
Balance at December 31, 2019	277.3		111.5		388.8
Acquisitions	2.5		—		2.5
Translation adjustments	0.1		2.8		2.9
Balance at December 31, 2020	$	279.9	$	114.3	$	394.2

The following table summarizes the gross carrying amount and accumulated amortization of intangible assets for each major class of intangible assets:


	2020						2019
(in millions)	Gross Carrying Value		Accumulated Amortization		Net Carrying Value		Gross Carrying Value		Accumulated Amortization		Net Carrying Value
Definite-lived intangible assets:
Customer relationships (a)	$	108.6	$	(29.6)	$	79.0	$	108.6	$	(20.5)	$	88.1
Other (a)	4.4		(2.3)		2.1		4.2		(1.6)		2.6
Total definite-lived intangible assets	113.0		(31.9)		81.1		112.8		(22.1)		90.7
Indefinite-lived intangible assets:
Trade names	72.4		—		72.4		72.2		—		72.2
Total indefinite-lived intangible assets	72.4		—		72.4		72.2		—		72.2
Total intangible assets	$	185.4	$	(31.9)	$	153.5	$	185.0	$	(22.1)	$	162.9

(a) Average useful life of customer relationships and other definite-lived intangible assets are estimated to be approximately 12 years and eight years, respectively. The average useful life across all definite-lived intangible assets is estimated to be approximately 12 years.

Amortization expense for the years ended December 31, 2020, 2019 and 2018 was $9.6 million, $8.8 million and $8.0 million respectively.

The Company currently estimates that aggregate amortization expense will be approximately $9.6 million in 2021, $9.5 million in 2022, $9.3 million in 2023, $9.3 million in 2024, $9.3 million in 2025 and $34.1 million thereafter. Actual amounts of amortization may differ from estimated amounts due to additional intangible asset acquisitions, changes in foreign currency rates, impairment of intangible assets and other events.