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Other Long-term Liabilities - Deferred Revenue (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Deferred Revenue and Other [Abstract]      
Deferred revenue $ 168.5 $ 172.0 $ 175.5
Deferred revenue recognized related to gas gathering and processing agreement $ 3.8 $ 3.9 3.9
Channelview Splitter [Member]      
Deferred Revenue and Other [Abstract]      
Deferred revenue     $ 129.0