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Retirement Benefits - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Jun. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Contributions to defined benefit pension plans $ 2.6 $ 2.4  
Contribution amounts expected to be paid for the remainder of the fiscal year 2017 $ 7.7    
Retirement Savings Plan [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Maximum employees contribution rate, pretax 50.00%    
Safe harbor non-elective contribution rate 3.00%    
Matching contribution by employer 50.00%    
Matching contribution rate 6.00%    
Matching and profit contribution vesting rate 25.00%    
SERP [Member] | Irrevocable Trust [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Retirement benefits total plan assets $ 94.7   $ 92.7
Surrender value of life insurance policies 41.0   40.8
SERP [Member] | Irrevocable Trust [Member] | Equity and Fixed Income Mutual Funds [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Available-for-sale securities 53.6   51.8
SERP [Member] | Cash and Cash Equivalents | Irrevocable Trust [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Retirement benefits cash and cash equivalents $ 0.1   $ 0.1