Intangible Assets

9 Months Ended

Sep. 30, 2024

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

(3) Intangible Assets

Intangible assets associated with customer relationships are amortized on a straight-line basis over the expected period of benefits of the customer relationships, which ranged from 10 to 20 years at the time the intangible assets were originally recorded. The weighted average amortization period for intangible assets is 14.9 years.

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

	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Nine Months Ended September 30, 2024
Customer relationships, beginning of period	$	1,844.8	$	(1,051.2)	$	793.6
Amortization expense	—		(95.6)		(95.6)
Customer relationships, end of period	$	1,844.8	$	(1,146.8)	$	698.0

Amortization expense was $31.9 million for each of the three months ended September 30, 2024 and 2023 and $95.6 million and $95.7 million for the nine months ended September 30, 2024 and 2023, respectively.

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

2024 (remaining)	$	32.0
2025	110.2
2026	106.3
2027	106.3
2028	106.3
Thereafter	236.9
Total	$	698.0