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Related Parties (Details) - Pension Plans, Defined Benefit - Investment Management Services for Defined Benefit Plan - Fayez Sarofim & Co. - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Related Party Transaction [Line Items]      
Assets managed by related party $ 149.3 $ 124.5 $ 171.8
Investment expenses from agreement with related party $ 0.9 $ 0.9 $ 0.9