Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligation Disclosure [Abstract]

Reconciliations of the Company's ARO liability

Reconciliations of the Company’s asset retirement obligations are as follows:

	Successor			Predecessor
	April 2 through December 31, 2017			January 1 through April 1, 2017			Year Ended December 31, 2016
	(Dollars in millions)
Balance at beginning of period	$	664.2		$	758.8		$	712.1
Liabilities settled or disposed	(65.2		)	(2.7		)	(41.5		)
Accretion expense	32.6			12.5			45.7
Revisions to estimates	59.5			(104.4		)	42.5
Balance at end of period	$	691.1		$	664.2		$	758.8
Less: Current portion (included in “Accounts payable and accrued expenses”)	34.1			31.1			41.0
Noncurrent obligation (included in “Asset retirement obligations”)	$	657.0		$	633.1		$	717.8
Balance at end of period — active locations	$	612.9		$	540.1		$	634.8
Balance at end of period — closed or inactive locations	$	78.2		$	124.1		$	124.0