Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax liabilities
Investments	$ 0	$ 0
Derivative contracts	0	0
Total deferred tax liabilities	0	0
Deferred tax assets
Property, plant and equipment	68,750	89,090
Net operating loss carryforwards	372,903	373,702
Tax credits and other carryforwards	33,851	33,852
Asset retirement obligations	13,551	13,791
Investments	121	165
Other	1,618	1,392
Total deferred tax assets	490,794	511,992
Valuation allowance	(440,225)	(447,463)
Net deferred tax asset	$ 50,569	$ 64,529