Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2018

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, 2018
Customer relationships, beginning of period	$	1,795.8	$	(298.7	)	$	1,497.1
Amortization expense	—		(61.7		)	(61.7		)
Customer relationships, end of period	$	1,795.8	$	(360.4	)	$	1,435.4

Schedule of Amortization Expense

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

2018 (remaining)	$	61.8
2019	123.4
2020	123.4
2021	123.4
2022	123.4
Thereafter	880.0
Total	$	1,435.4