Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies (Details)

v3.21.1
Summary of Significant Accounting Policies (Details) - USD ($)
$ in Millions
Mar. 31, 2021
Dec. 31, 2020
Sep. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Oct. 01, 2019
Sep. 30, 2019
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]              
Stockholders' equity $ 1,235.7 $ 1,206.3 $ 1,079.4 $ 1,027.0 $ 1,143.8   $ 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 603.1 541.4 481.4 496.4 586.5   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 $ (85.8) $ (40.7) $ (102.8) $ (158.3) $ (126.7)   (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