Asset Retirement Obligations (Tables)

3 Months Ended

Mar. 31, 2017

Asset Retirement Obligation Disclosure [Abstract]

Summary of Changes in Asset Retirement Obligations

The schedule below summarizes the changes in our asset retirement obligations (in millions):

Three Months Ended March 31, 2017
Balance, beginning of period	$	13.5
Accretion expense	0.2
Balance, end of period	$	13.7