Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies (Details)

v3.21.2
Summary of Significant Accounting Policies (Details) - USD ($)
$ in Millions
Jun. 30, 2021
Mar. 31, 2021
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Oct. 01, 2019
Sep. 30, 2019
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]              
Stockholders' equity $ 1,252.4 $ 1,235.7 $ 1,079.4 $ 1,055.1 $ 1,027.0   $ 769.8
Cumulative Effect, Period of Adoption, Adjustment              
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]              
Stockholders' equity             0.0
Retained Earnings [Member]              
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]              
Stockholders' equity 627.1 603.1 481.4 504.4 496.4   599.5
Retained Earnings [Member] | Cumulative Effect, Period of Adoption, Adjustment              
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]              
Stockholders' equity             6.0
Retained Earnings [Member] | Accounting Standards Update 2018-02 [Member] | Cumulative Effect, Period of Adoption, Adjustment              
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]              
Stockholders' equity           $ 6.0  
AOCI Attributable to Parent [Member]              
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]              
Stockholders' equity $ (55.2) $ (85.8) $ (102.8) $ (142.6) $ (158.3)   (140.6)
AOCI Attributable to Parent [Member] | Cumulative Effect, Period of Adoption, Adjustment              
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]              
Stockholders' equity             $ (6.0)
AOCI Attributable to Parent [Member] | Accounting Standards Update 2018-02 [Member] | Cumulative Effect, Period of Adoption, Adjustment              
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]              
Stockholders' equity           $ 6.0