Derivative Instruments - Narrative (Details) MMBTU in Millions	1 Months Ended		3 Months Ended		6 Months Ended
	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) MMBTU	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) MMBTU	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Apr. 30, 2019 USD ($)
Derivative [Line Items]
Change in unrealized gain (loss) on hedged item					$ (14,237,000)	$ 0
Cash Received (Paid) in Settlement of Commodity Derivative Instruments:			$ 142,256,000	$ 10,672,000	293,417,000	(30,710,000)
Interest Rate Swap
Derivative [Line Items]
Derivative notional amount			581,218,000		581,218,000		$ 160,000,000
Interest Rate Swap | Interest Expense
Derivative [Line Items]
Cash (paid) received on settlement of derivatives			(536,000)		(592,000)
Change in unrealized gain (loss) on hedged item			(3,598,000)		(14,237,000)
Gain (loss) on derivative, net			(4,134,000)		(14,829,000)
Interest Rate Swap on Revolving Credit Facility | Long
Derivative [Line Items]
Term of derivative contract	4 years
Put option	0.00%
Derivative notional amount	$ 250,000,000		$ 250,000,000		$ 250,000,000
Interest Rate Swap On Line Of Credit | Long
Derivative [Line Items]
Put option			0.25%		0.25%
NYMEX Natural Gas Hedges | Natural Gas
Derivative [Line Items]
Cash Received (Paid) in Settlement of Commodity Derivative Instruments:			$ 29,015,000
Nonmonetary notional amount | MMBTU			39		39
NYMEX Commodity Swaps | Natural Gas
Derivative [Line Items]
Cash Received (Paid) in Settlement of Commodity Derivative Instruments:					$ 54,982,000
Line of Credit
Derivative [Line Items]
Credit facility, face amount	$ 175,000,000
Revolving Credit Facility
Derivative [Line Items]
Credit facility, face amount		$ 160,000,000		$ 160,000,000		$ 160,000,000		$ 2,100,000,000
Credit facility, modification period		3 years