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Derivative Instruments Derivative Instruments (Balance Sheet Offsetting) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Balance Sheet Offsetting [Line Items] |  |  |
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement |  | $ 89,889 | $ 105,674
Derivative Asset, Amount Offset by Liabiilty |  | 0 | 0
Derivative Assets | [1] | 89,889 | 105,674
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement |  | 18,675 | 10,219
Derivative Liability, Amount Offset by Asset |  | 0 | 0
Derivative Liability | [1] | 18,675 | 10,219
Derivative Subject to Master Netting Agreement [Member] |  |  |
Balance Sheet Offsetting [Line Items] |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 86,497 | 105,147
Derivative Asset, Amount Offset by Liabiilty |  | 0 | 0
Derivative Asset, Noncurrent |  | 86,497 | 105,147
Derivative Asset, Not Offset, Policy Election Deduction |  | (108) | (8,104)
Derivative Asset, Fair Value of Collateral |  | 0 | (59,525)
Derivative Asset, Fair Value, Amount Offset Against Collateral |  | 86,389 | 37,518
Derivative Liability, Fair Value, Gross Liability |  | 18,420 | 10,083
Derivative Liability, Amount Offset by Asset |  | 0 | 0
Derivative Liability, Noncurrent |  | 18,420 | 10,083
Derivative Liability, Not Offset, Policy Election Deduction |  | (108) | (8,104)
Derivative Liability, Fair Value of Collateral |  | (16,738) | (437)
Derivative Liability, Fair Value, Amount Offset Against Collateral |  | 1,574 | 1,542
Derivative Not Subject to Master Netting Agreement [Member] |  |  |
Balance Sheet Offsetting [Line Items] |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 3,392 | 527
Derivative Asset, Amount Offset by Liabiilty |  | 0 | 0
Derivative Asset, Not Subject to Master Netting Arrangement |  | 3,392 | 527
Derivative Liability, Fair Value, Gross Liability |  | 255 | 136
Derivative Liability, Amount Offset by Asset |  | 0 | 0
Derivative Liability, Not Subject to Master Netting Arrangement |  | $ 255 | $ 136
[1] | The fair value of each class of derivative is shown in Note 19.

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