Carryforwards (Details 4) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
State and local jurisdiction
Carryforwards [Line Items]
Operating loss carryforwards	$ 151.5	$ 149.8
Investment tax credit carryforward, amount	36.3	37.4
Federal and State Taxing Authority
Carryforwards [Line Items]
Tax credit carryforward, amount	$ 37.1	$ 43.7