Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables	3 Months Ended
Mar. 31, 2019
Gas Balancing Arrangements [Abstract]
Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables	Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables The operating subsidiaries of the Partnership provide storage services whereby they store natural gas or NGLs on behalf of customers and also periodically hold customer gas under parking and lending (PAL) services. Since the customers retain title to the gas held by the Partnership in providing these services, the Partnership does not record the related gas on its balance sheet. The operating subsidiaries of the Partnership also periodically lend gas to customers under PAL and certain firm services, and gas or NGLs may be owed to the operating subsidiaries as a result of transportation imbalances. As of March 31, 2019, the amount of gas owed to the operating subsidiaries of the Partnership due to gas imbalances and gas loaned under PAL and certain firm service agreements was approximately 32.3 trillion British thermal units (TBtu). Assuming an average market price during March 2019 of $2.83 per million British thermal unit (MMBtu), the market value of that gas was approximately $91.4 million. As of March 31, 2019, the amount of NGLs owed to the Partnership's operating subsidiaries due to imbalances was approximately 0.2 million barrels, which had a market value of approximately $3.4 million dollars. As of December 31, 2018, the amount of gas owed to the operating subsidiaries due to gas imbalances and gas loaned under PAL and certain firm service agreements was approximately 13.5 TBtu. Assuming an average market price during December 2018 of $3.68 per MMBtu, the market value of that gas was approximately $49.7 million. As of December 31, 2018, there were no outstanding NGL imbalances owed to the operating subsidiaries. If any significant customer should have credit or financial problems resulting in a delay or failure to repay the gas owed to the operating subsidiaries, it could have a material adverse effect on the Partnership’s financial condition, results of operations or cash flows.

Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables

3 Months Ended

Mar. 31, 2019

Gas Balancing Arrangements [Abstract]

Gas and Liquids Stored Underground and Gas and NGLs Receivables and Payables

The operating subsidiaries of the Partnership provide storage services whereby they store natural gas or NGLs on behalf of customers and also periodically hold customer gas under parking and lending (PAL) services. Since the customers retain title to the gas held by the Partnership in providing these services, the Partnership does not record the related gas on its balance sheet.

The operating subsidiaries of the Partnership also periodically lend gas to customers under PAL and certain firm services, and gas or NGLs may be owed to the operating subsidiaries as a result of transportation imbalances. As of March 31, 2019, the amount of gas owed to the operating subsidiaries of the Partnership due to gas imbalances and gas loaned under PAL and certain firm service agreements was approximately 32.3 trillion British thermal units (TBtu). Assuming an average market price during March 2019 of $2.83 per million British thermal unit (MMBtu), the market value of that gas was approximately $91.4 million. As of March 31, 2019, the amount of NGLs owed to the Partnership's operating subsidiaries due to imbalances was approximately 0.2 million barrels, which had a market value of approximately $3.4 million dollars. As of December 31, 2018, the amount of gas owed to the operating subsidiaries due to gas imbalances and gas loaned under PAL and certain firm service agreements was approximately 13.5 TBtu. Assuming an average market price during December 2018 of $3.68 per MMBtu, the market value of that gas was approximately $49.7 million. As of December 31, 2018, there were no outstanding NGL imbalances owed to the operating subsidiaries. If any significant customer should have credit or financial problems resulting in a delay or failure to repay the gas owed to the operating subsidiaries, it could have a material adverse effect on the Partnership’s financial condition, results of operations or cash flows.