Intangible Assets (Tables)

6 Months Ended

Jun. 30, 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 (in millions):

	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Six Months Ended June 30, 2021
Customer relationships, beginning of period	$	1,794.2	$	(668.8)	$	1,125.4
Customer relationships obtained from acquisition of business	57.3		—		57.3
Amortization expense	—		(62.5)		(62.5)
Customer relationships, end of period	$	1,851.5	$	(731.3)	$	1,120.2

Schedule of Amortization Expense

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

2021 (remaining)	$	64.1
2022	128.2
2023	128.2
2024	128.2
2025	110.8
Thereafter	560.7
Total	$	1,120.2