Asset Retirement Obligation (Notes)

3 Months Ended

Mar. 31, 2014

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

(9)Asset Retirement Obligations

The schedule below summarizes the changes in the Company’s asset retirement obligations:

	March 31, 2014		March 31, 2013
	(in millions)
Beginning asset retirement obligations	$	7.7	$	9.1
Revisions to existing liabilities	—		0.4
Liabilities acquired	0.5		—
Accretion	0.2		0.1
Ending asset retirement obligations	$	8.4	$	9.6