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Derivatives (Derivatives Not Designated as Hedging Instruments - Commodity Contracts) (Details) MMBTU in Thousands, Boe in Thousands, $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2021 USD ($) MMBTU Boe | Dec. 31, 2020 USD ($) MMBTU Boe
Derivative [Line Items] |  |
Derivative assets - Fair value | $ 694,010 | $ 602,754
Derivative liabilities - Fair value | $ 561,788 | $ 424,828
Customer Counterparty | Crude oil |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | Boe | 8,557 | 6,321
Customer Counterparty | Natural gas |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | MMBTU | 95,273 | 109,635
Derivatives not designated as hedging instruments |  |
Derivative [Line Items] |  |
Derivative assets - Fair value | $ 693,852 | $ 602,754
Derivative liabilities - Fair value | 560,639 | 422,729
Derivatives not designated as hedging instruments | Commodity contracts |  |
Derivative [Line Items] |  |
Derivative assets - Fair value | 363,063 | 82,451
Derivative liabilities - Fair value | 324,027 | 84,165
Commodity contracts | Derivatives not designated as hedging instruments | Customer Counterparty | Commodity contracts |  |
Derivative [Line Items] |  |
Derivative assets - Fair value | 256,001 | 44,763
Derivative liabilities - Fair value | $ 14,821 | $ 43,978
Commodity contracts | Derivatives not designated as hedging instruments | Customer Counterparty | Crude oil | Written options |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | Boe | 212 |
Derivative assets - Fair value | $ 302 |
Derivative liabilities - Fair value | $ 1 |
Commodity contracts | Derivatives not designated as hedging instruments | Customer Counterparty | Crude oil | Collars |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | Boe | 3,070 | 2,022
Derivative assets - Fair value | $ 35,941 | $ 2,344
Derivative liabilities - Fair value | $ 0 | $ 2,193
Commodity contracts | Derivatives not designated as hedging instruments | Customer Counterparty | Crude oil | Swaps |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | Boe | 5,275 | 4,299
Derivative assets - Fair value | $ 82,563 | $ 9,282
Derivative liabilities - Fair value | $ 2 | $ 14,283
Commodity contracts | Derivatives not designated as hedging instruments | Customer Counterparty | Crude oil | Commodity contracts |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | Boe | 8,557 | 6,321
Derivative assets - Fair value | $ 118,806 | $ 11,626
Derivative liabilities - Fair value | $ 3 | $ 16,476
Commodity contracts | Derivatives not designated as hedging instruments | Customer Counterparty | Natural gas | Written options |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | MMBTU | 2,668 | 597
Derivative assets - Fair value | $ 0 | $ 0
Derivative liabilities - Fair value | $ 0 | $ 59
Commodity contracts | Derivatives not designated as hedging instruments | Customer Counterparty | Natural gas | Collars |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | MMBTU | 25,224 | 12,733
Derivative assets - Fair value | $ 30,542 | $ 1,063
Derivative liabilities - Fair value | $ 62 | $ 205
Commodity contracts | Derivatives not designated as hedging instruments | Customer Counterparty | Natural gas | Swaps |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | MMBTU | 67,381 | 96,305
Derivative assets - Fair value | $ 106,653 | $ 32,074
Derivative liabilities - Fair value | $ 14,756 | $ 27,238
Commodity contracts | Derivatives not designated as hedging instruments | Customer Counterparty | Natural gas | Commodity contracts |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | MMBTU | 95,273 | 109,635
Derivative assets - Fair value | $ 137,195 | $ 33,137
Derivative liabilities - Fair value | 14,818 | 27,502
Commodity contracts | Derivatives not designated as hedging instruments | Financial Counterparty | Commodity contracts |  |
Derivative [Line Items] |  |
Derivative assets - Fair value | 107,062 | 37,689
Derivative liabilities - Fair value | $ 309,206 | $ 40,187
Commodity contracts | Derivatives not designated as hedging instruments | Financial Counterparty | Crude oil | Purchased options |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | Boe | 212 |
Derivative assets - Fair value | $ 0 |
Derivative liabilities - Fair value | $ 278 |
Commodity contracts | Derivatives not designated as hedging instruments | Financial Counterparty | Crude oil | Collars |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | Boe | 3,126 | 2,022
Derivative assets - Fair value | $ 0 | $ 2,217
Derivative liabilities - Fair value | $ 35,575 | $ 2,402
Commodity contracts | Derivatives not designated as hedging instruments | Financial Counterparty | Crude oil | Swaps |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | Boe | 8,219 | 4,299
Derivative assets - Fair value | $ 30,604 | $ 8,220
Derivative liabilities - Fair value | $ 98,712 | $ 7,135
Commodity contracts | Derivatives not designated as hedging instruments | Financial Counterparty | Crude oil | Commodity contracts |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | Boe | 11,557 | 6,321
Derivative assets - Fair value | $ 30,604 | $ 10,437
Derivative liabilities - Fair value | $ 134,565 | $ 9,537
Commodity contracts | Derivatives not designated as hedging instruments | Financial Counterparty | Natural gas | Purchased options |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | MMBTU | 2,668 | 597
Derivative assets - Fair value | $ 0 | $ 59
Derivative liabilities - Fair value | $ 0 | $ 0
Commodity contracts | Derivatives not designated as hedging instruments | Financial Counterparty | Natural gas | Collars |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | MMBTU | 29,242 | 16,293
Derivative assets - Fair value | $ 5,236 | $ 205
Derivative liabilities - Fair value | $ 32,005 | $ 813
Commodity contracts | Derivatives not designated as hedging instruments | Financial Counterparty | Natural gas | Swaps |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | MMBTU | 127,419 | 103,973
Derivative assets - Fair value | $ 71,222 | $ 26,988
Derivative liabilities - Fair value | $ 142,636 | $ 29,837
Commodity contracts | Derivatives not designated as hedging instruments | Financial Counterparty | Natural gas | Commodity contracts |  |
Derivative [Line Items] |  |
Derivative, nonmonetary notional amount, energy measure | MMBTU | 159,329 | 120,863
Derivative assets - Fair value | $ 76,458 | $ 27,252
Derivative liabilities - Fair value | $ 174,641 | $ 30,650

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