Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables (Details) MMBbls in Millions, MMBTU in Millions, $ in Millions	Sep. 30, 2020 USD ($) $ / MMBTU MMBTU MMBbls	Dec. 31, 2019 USD ($) $ / MMBTU MMBTU MMBbls
Gas Balancing Arrangements [Abstract]
Gas Balancing Measurement (in MMBtu) | MMBTU	7.0	12.8
Average Market Price of Gas Assumed | $ / MMBTU	1.71	2.08
Gas Imbalance Asset Liability	$ 12.0	$ 26.6
Natural Gas Liquids Balancing Volume (in MMbbls) (Less than) | MMBbls	0.1	0.0
Natural Gas Liquids Imbalance to Subsidiaries Asset Liability	$ 0.4