Income Taxes - Income Tax Expense (Benefit) (Details) - USD ($)
$ in Millions
7 Months Ended 12 Months Ended
Jun. 30, 2015
Feb. 01, 2015
Jun. 30, 2017
Jun. 30, 2016
Current:        
Federal $ (0.2)   $ 16.8 $ 18.4
State 0.6   3.6 5.0
Deferred:        
Federal (11.4)   (16.0) (17.4)
State (1.6)   (1.8) (2.2)
Total income tax expense (benefit) $ (12.6)   $ 2.6 $ 3.8
Predecessor [Member]        
Current:        
Federal   $ (1.7)    
State   1.4    
Deferred:        
Federal   4.4    
State   (0.9)    
Total income tax expense (benefit)   $ 3.2