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Organization and Summary of Significant Accounting Policies - Maintenance, Repair and Operations (MRO) Materials (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Maintenance, Repair and Operations (MRO) Materials [Abstract]      
Maintenance, Repair and Operations (MRO) Materials Amortization $ 67.7 $ 62.4 $ 51.6