Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Schedule of financial assets and liabilities (Details)

v3.19.2
Fair Value Measurements - Schedule of financial assets and liabilities (Details) - USD ($)
$ in Millions
Jun. 30, 2019
Sep. 30, 2018
Jun. 30, 2018
Financial assets and liabilities at carrying value and fair value      
Cash and cash equivalents $ 64.4 $ 56.0 $ 71.1
Level 1      
Assets:      
Cash and cash equivalents 64.4    
Investments in rabbi trust 4.2    
Derivative instruments 0.0    
Liabilities:      
Derivative instruments 0.0    
Level 2      
Assets:      
Cash and cash equivalents 0.0    
Investments in rabbi trust 0.0    
Derivative instruments 2.0    
Liabilities:      
Derivative instruments 17.7    
Level 3      
Assets:      
Cash and cash equivalents 0.0    
Investments in rabbi trust 0.0    
Derivative instruments 0.0    
Liabilities:      
Derivative instruments 0.0    
$150 senior unsecured notes      
Assets:      
Long-term Debt, Gross 149.7    
$150 senior unsecured notes | Level 1      
Liabilities:      
Debt instruments 154.2    
$150 senior unsecured notes | Level 2      
Liabilities:      
Debt instruments 0.0    
$150 senior unsecured notes | Level 3      
Liabilities:      
Debt instruments 0.0    
$900 revolving credit facility (excluding outstanding letters of credit)      
Assets:      
Long-term Debt, Gross 74.0    
$900 revolving credit facility (excluding outstanding letters of credit) | Level 1      
Liabilities:      
Debt instruments 0.0    
$900 revolving credit facility (excluding outstanding letters of credit) | Level 2      
Liabilities:      
Debt instruments 74.0    
$900 revolving credit facility (excluding outstanding letters of credit) | Level 3      
Liabilities:      
Debt instruments 0.0    
$100 Series A Notes      
Assets:      
Long-term Debt, Gross 100.0    
$100 Series A Notes | Level 1      
Liabilities:      
Debt instruments 0.0    
$100 Series A Notes | Level 2      
Liabilities:      
Debt instruments 106.1    
$100 Series A Notes | Level 3      
Liabilities:      
Debt instruments 0.0    
Interest Rate Swap [Member] | Cash flow hedging      
Financial assets and liabilities at carrying value and fair value      
Derivative, notional amount 150.0    
Derivatives | Cash flow hedging      
Financial assets and liabilities at carrying value and fair value      
Derivative, notional amount 306.8    
Reported Value Measurement      
Assets:      
Investments in rabbi trust 4.2    
Derivative instruments 2.0    
Liabilities:      
Derivative instruments $ 17.7