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Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2017
Asset Retirement Obligation Disclosure [Abstract]  
Activity For Asset Retirement Obligations

The following table presents activity for asset retirement obligations for the years ended December 31, 2017 and 2016

 

 

 

 

 

 

 

Year Ended December 31, 

(In millions)

2017

 

2016

Balance, beginning of period

$

5.3

 

$

5.0

Revisions and liabilities incurred

 

0.3

 

 

0.2

Accretion expense

 

0.4

 

 

0.4

Payments

 

(0.2)

 

 

(0.3)

Balance, end of period

$

5.8

 

$

5.3