Accounting for Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Asset Retirement Obligations

A reconciliation of our AROs is as follows:

	Years Ended December 31,
(in millions)	2017			2016
AROs, beginning of period	$	849.9		$	841.6
Liabilities incurred	27.1			28.0
Liabilities settled	(64.8		)	(67.4		)
Accretion expense	25.7			40.4
Revisions in estimated cash flows	15.7			5.8
Foreign currency translation	5.7			1.5
AROs, end of period	859.3			849.9
Less current portion	98.1			102.0
	$	761.2		$	747.9