Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of Changes in Carrying Value

The following table represents our change in carrying value of intangible assets for the periods stated (in millions):

	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Year Ended December 31, 2021
Customer relationships, beginning of period	$	1,794.2	$	(668.8)	$	1,125.4
Customer relationships obtained from acquisition of business	50.6		—		50.6
Amortization expense	—		(126.3)		(126.3)
Customer relationships, end of period	$	1,844.8	$	(795.1)	$	1,049.7
Year Ended December 31, 2020
Customer relationships, beginning of period	$	1,795.8	$	(545.9)	$	1,249.9
Amortization expense	—		(123.5)		(123.5)
Retirements (1)	(1.6)		0.6		(1.0)
Customer relationships, end of period	$	1,794.2	$	(668.8)	$	1,125.4
Year Ended December 31, 2019
Customer relationships, beginning of period	$	1,795.8	$	(422.2)	$	1,373.6
Amortization expense	—		(123.7)		(123.7)
Customer relationships, end of period	$	1,795.8	$	(545.9)	$	1,249.9

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(1)Intangible assets retired as a result of the disposition of certain non-core assets.

Schedule of Amortization Expense

The following table summarizes our estimated aggregate amortization expense for the next five years and thereafter (in millions):

2022	$	127.6
2023	127.6
2024	127.6
2025	110.3
2026	106.4
Thereafter	450.2
Total	$	1,049.7