Long-Term Debt - Outstanding Long-Term Debt (Detail) - USD ($) $ in Thousands		May 05, 2020		Mar. 31, 2020		Dec. 31, 2019
Debt Instrument [Line Items]
Total long-term debt				$ (456,600)		$ (486,600)
Debt Instrument, Unused Borrowing Capacity, Amount		$ 310,000		10,000
Debt Instrument, Unused Borrowing Capacity, Subsequent		300,000
Total Long-term debt				455,783		485,768
Less: current maturities				(15,600)		(45,600)
Less: debt issuance costs				808		822
Total long-term debt, net of current maturities				440,183		440,168
Aggregated Unfunded Commitments [Member]
Debt Instrument [Line Items]
Total long-term debt		(90,000)		(90,000)
New York Life [Member]
Debt Instrument [Line Items]
Total long-term debt	[1]			(100,000)
9.08% bond, due June 1, 2022 [Member]
Debt Instrument [Line Items]
Total long-term debt	[2]			(7,991)		(7,990)
5.50% note, due October 12, 2020 [Member]
Debt Instrument [Line Items]
Total long-term debt				(2,000)		(2,000)
5.93% note, due October 31, 2023 [Member]
Debt Instrument [Line Items]
Total long-term debt				(12,000)		(12,000)
5.68% note, due June 30, 2026 [Member]
Debt Instrument [Line Items]
Total long-term debt				(20,300)		(20,300)
6.43% note, due May 2, 2028 [Member]
Debt Instrument [Line Items]
Total long-term debt				(6,300)		(6,300)
3.73% note, due December 16, 2028 [Member]
Debt Instrument [Line Items]
Total long-term debt				(18,000)		(18,000)
3.88% note, due May 15, 2029 [Member]
Debt Instrument [Line Items]
Total long-term debt				(50,000)		(50,000)
3.25% note, due April 30, 2032 [Member]
Debt Instrument [Line Items]
Total long-term debt				(70,000)		(70,000)
3.48% note, due May 31, 2038 [Member]
Debt Instrument [Line Items]
Total long-term debt				(50,000)		(50,000)
Uncollateralized Senior Note Due November Two Thousand Thirty Eight [Member]
Debt Instrument [Line Items]
Total long-term debt				(50,000)		(50,000)
Uncollateralized Senior Note Due August Two Thousand Thirty Nine [Member]
Debt Instrument [Line Items]
Total long-term debt				(100,000)		(100,000)
Term Note Due January Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Total long-term debt				(70,000)		(70,000)
Term Note Due February Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Total long-term debt				0		$ (30,000)
Aggregate Shelf Agreements [Member]
Debt Instrument [Line Items]
Total long-term debt		(270,000)		(270,000)
Aggregate Shelf Agreements [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		670,000		370,000
Debt Instrument, Face Amount, Subsequent		300,000
Prudential [Member]
Debt Instrument [Line Items]
Total long-term debt	[3]			(170,000)
Debt Instrument, Unused Borrowing Capacity, Amount		150,000	[4]	0	[3]
Prudential [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		150,000	[4]	220,000	[3]
MetLife [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[5]	150,000
Debt Instrument, Unused Borrowing Capacity, Amount		$ 150,000	[5]	150,000
New York Life [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				100,000
Debt Instrument, Unused Borrowing Capacity, Amount	[1]			10,000
New York Life [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[1]			$ 150,000

[1] ⁽²⁾ In February 2020, we requested and NYL accepted our request to purchase $40.0 million of our unsecured debt.

[2] FPU secured first mortgage bonds are guaranteed by Chesapeake Utilities.

[3] ⁽¹⁾ In January 2020, we requested and Prudential accepted our request to purchase $50.0 million of our unsecured debt.

[4] ⁽³⁾ In April 2020, the Prudential Shelf Agreement was amended to reinstate and increase the available borrowing capacity back to $150.0 million.

[5] ⁽⁴⁾ In April 2020, we agreed to commercial terms with MetLife to provide a new $150.0 million MetLife Shelf Agreement for a three-year term ending March 31, 2023. The MetLife Shelf Agreement will be finalized in May 2020.