Asset Retirement Obligations (Tables)

3 Months Ended

Mar. 31, 2015

Asset Retirement Obligations [Abstract]

Changes in Aggregate Asset Retirement Obligations

The changes in our aggregate asset retirement obligations are as follows:

	Three Months Ended March 31, 2015
Beginning of period	$	57.3
Fair value of ARO acquired with Atlas mergers		4.1
Change in cash flow estimate		3.7
Accretion expense		1.3
End of period	$	66.4