Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.1
Fair Value Measurements - Schedule of financial assets and liabilities (Details) - USD ($)
$ in Millions
Mar. 31, 2019
Sep. 30, 2018
Mar. 31, 2018
Financial assets and liabilities at carrying value and fair value      
Cash and cash equivalents $ 58.6 $ 56.0 $ 68.5
Level 1      
Assets:      
Cash and cash equivalents 58.6    
Investments in rabbi trust 4.0    
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 2.2    
Liabilities:      
Derivative instruments 12.4    
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 149.8    
$150 senior unsecured notes | Level 1      
Liabilities:      
Debt instruments 154.0    
$150 senior unsecured notes | Level 2      
Liabilities:      
Debt instruments 0.0    
$150 senior unsecured notes | Level 3      
Liabilities:      
Debt instruments 0.0    
Revolving credit facility      
Assets:      
Long-term Debt, Gross 112.6    
Revolving credit facility | Level 1      
Liabilities:      
Debt instruments 0.0    
Revolving credit facility | Level 2      
Liabilities:      
Debt instruments 112.6    
Revolving credit facility | 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 105.4    
$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 0.0    
Derivatives | Cash flow hedging      
Financial assets and liabilities at carrying value and fair value      
Derivative, notional amount 283.3    
Reported Value Measurement      
Assets:      
Investments in rabbi trust 4.0    
Derivative instruments 2.2    
Liabilities:      
Derivative instruments $ 12.4