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Basis of Presentation (Tables)
 12 Months Ended
Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Schedule of asset retirement obligation
The activities and balances for ARO are as follows (in millions):
 
Balance at Beginning of Period
 
Liabilities Incurred
 
Liabilities Settled
 
Accretion Expense
 
Revisions to Estimates
 
Balance at End of Period
Year ended June 30, 2018
$
3.6

 
$
0.7

 
$
(0.2
)
 
$
0.1

 
$
(0.5
)
 
$
3.7

Year ended July 1, 2017
$
3.7

 
$
0.1

 
$
(0.1
)
 
$
0.2

 
$
(0.3
)
 
$
3.6