Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

The table below provides a summary of our change in carrying amount of goodwill (in millions) for the year ended December 31, 2016, by assigned reporting unit:

	Texas			Oklahoma		Crude and Condensate			Corporate			Totals
Year Ended December 31, 2016
Balance, beginning of period	$	703.5		$	190.3	$	93.2		$	1,426.9		$	2,413.9
Impairment	(473.1		)	—		(93.2		)	(307.0		)	(873.3		)
Acquisition adjustment	1.6			—		—			—			1.6
Balance, end of period	$	232.0		$	190.3	$	—		$	1,119.9		$	1,542.2

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, 2017
Customer relationships, beginning of period	$	1,795.8	$	(171.6	)	$	1,624.2
Amortization expense	—		(127.1		)	(127.1		)
Customer relationships, end of period	$	1,795.8	$	(298.7	)	$	1,497.1
Year Ended December 31, 2016
Customer relationships, beginning of period	$	744.5	$	(54.6	)	$	689.9
Acquisitions	1,051.3		—			1,051.3
Amortization expense	—		(117.0		)	(117.0		)
Customer relationships, end of period	$	1,795.8	$	(171.6	)	$	1,624.2

Schedule of Amortization Expense

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

2018	$	123.4
2019	123.4
2020	123.4
2021	123.4
2022	123.4
Thereafter	880.1
Total	$	1,497.1