Derivative Activities - Additional Information (Detail)	Mar. 31, 2019 USD ($) t_per_M MMBTU bbl
Derivatives Excluding Basis Swaps and Freight Swaps
Derivative [Line Items]
Derivative assets liabilities at fair value net	$ 3,000,000
Commodity | Natural Gas Basis Swaps
Derivative [Line Items]
Derivative assets liabilities at fair value net	$ (3,400,000)
Volume Hedged | MMBTU	69,775,000
Commodity | Propane Spread Swaps
Derivative [Line Items]
Derivative assets liabilities at fair value net	$ (809,000)
Volume Hedged | bbl	1,875,000
Commodity | Swaps | Freight | Level 2
Derivative [Line Items]
Derivative assets liabilities at fair value net	$ (103,000)
Volume Hedged | t_per_M	10,000