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Fair Value Measurements - Nonrecurring Fair Value Measurements (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Fair Value Disclosures [Abstract]        
Asset impairments $ 0.0 $ 0.0 $ 4.7 $ 18.6