Derivative Instruments - Additional Information (Detail) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Feb. 28, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) gal	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current		$ 127	$ 127	$ 1,844
Unrealized Gain (Loss) on Derivatives			7,505	910	$ (2,701)
Notional Amount of Nonderivative Instruments		$ 60,000	$ 100,000
Number of short-term lines of Credit, rate swap			3
Subsequent Event
Derivative [Line Items]
Notional Amount of Nonderivative Instruments	$ 40,000
Fixed Swap Rate	0.17%
Interest Rate Swap Rate, Low Range [Member]
Derivative [Line Items]
Fixed Swap Rate		0.20%	0.2615%
Interest Rate Swap Rate, High Range [Member]
Derivative [Line Items]
Fixed Swap Rate		0.205%	0.3875%
Interest Rate Swap [Member]
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			$ 100
Derivatives designated as fair value hedges | Mark To Market Energy Assets | Put Option
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current		$ 23	23
Derivatives designated as fair value hedges | Mark-to-market energy liabilities | Propane Swap Agreement
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current		64	64	1,844
Derivatives designated as fair value hedges | Mark-to-market energy liabilities | Interest Rate Swap [Member]
Derivative [Line Items]
Energy Marketing Contract Liabilities, Current		40	40
Sharp Energy Inc [Member]
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			2,700
Other Receivables from Broker-Dealers and Clearing Organizations		0	0	2,317
Other Payables to Broker-Dealers and Clearing Organizations		$ 1,505	$ 1,505
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimate of Time to Transfer			12 months
Sharp Energy Inc [Member] | Put Or Call Option [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal			400,000
Other Comprehensive Income (Loss) | Derivatives designated as fair value hedges | Natural Gas Futures [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			$ 0	(294)	532
Other Comprehensive Income (Loss) | Derivatives designated as fair value hedges | Natural Gas Swaps [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			0	(63)	200
Other Comprehensive Income (Loss) | Derivatives designated as fair value hedges | Propane Swap Agreement
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			5,035	(253)	(2,773)
Other Comprehensive Income (Loss) | Derivatives designated as fair value hedges | Interest Rate Swap [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			(40)
Cost of Sales [Member] | Not Designated as Hedging Instrument [Member] | Propane Swap Agreement
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net			0	0	(13)
Cost of Sales [Member] | Derivatives designated as fair value hedges | Propane Swap Agreement
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net			2,428	1,520	(647)
Cost of Sales [Member] | Derivatives designated as fair value hedges | Put Or Call Option [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net			(12)	$ 0	$ 0
Inventories [Member] | Derivatives designated as fair value hedges | Put Or Call Option [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net			34
Interest Expense | Derivatives designated as fair value hedges | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net			$ 60