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Asset Retirement Obligations
 3 Months Ended
Mar. 31, 2017
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations
(10) 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



Asset retirement obligations of $13.7 million and $13.5 million were included in “Asset retirement obligations” as non-current liabilities on the consolidated balance sheets as of March 31, 2017 and December 31, 2016, respectively.