XML 96 R69.htm IDEA: XBRL DOCUMENT v3.20.4
Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Deferred tax liabilities    
Investments $ 34,816 $ 109,289
Derivative contracts 0 29
Total deferred tax liabilities 34,816 109,318
Deferred tax assets    
Property, plant and equipment 317,063 300,704
Net operating loss carryforwards 365,772 383,418
Tax credits and other carryforwards 33,538 34,148
Asset retirement obligations 15,216 18,747
Other 2,500 2,290
Total deferred tax assets 734,089 739,307
Valuation allowance (699,273) (629,989)
Net deferred tax liability $ 0 $ 0