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Components of net periodic benefit cost (Details 3) - Qualified Plan - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Underfunded Plan | Pension Benefits |  |  |
Components of net periodic benefit cost (credit): |  |  |
Service cost | $ 0 | $ 0 | $ 0
Interest cost | 9,819 | 12,093 | 15,225
Expected return on assets | (19,576) | (19,949) | (18,236)
Amortization of prior service credit | 0 | 0 | 0
Recognized net actuarial loss | 8,017 | 7,172 | 5,548
Net periodic benefit cost (credit), including amount capitalized | (1,740) | (684) | 2,537
Less amount capitalized | 0 | 0 | 0
Net periodic benefit cost (credit) | (1,740) | (684) | 2,537
Other changes in plan assets and benefit obligations recognized in accumulated comprehensive loss: |  |  |
Net (gain) loss | (265) | 934 | (144)
Amortization of actuarial loss | (1,286) | (1,155) | (904)
Amortization of prior service credit | 0 | 0 | 0
Total recognized in accumulated other comprehensive loss | (1,551) | (221) | (1,048)
Other changes in plan assets and benefit obligations recognized in regulatory assets or liabilities: |  |  |
Net (gain) loss | (5,116) | 4,546 | 189
Amortization of actuarial gain (loss) | (6,731) | (6,017) | (4,644)
Amortization of prior service credit | 0 | 0 | 0
Total recognized in regulatory assets or liabilities | (11,847) | (1,471) | (4,455)
Total recognized in net periodic benefit cost (credit), accumulated other comprehensive loss and regulatory assets or liabilities | (15,138) | (2,376) | (2,966)
Overfunded Plan | Other Postretirement Benefits |  |  |
Components of net periodic benefit cost (credit): |  |  |
Service cost | 1,600 | 1,532 | 1,142
Interest cost | 1,862 | 2,437 | 2,986
Expected return on assets | (5,098) | (5,019) | (4,804)
Amortization of prior service credit | (1,398) | (1,398) | (1,398)
Recognized net actuarial loss | 24 | 287 | 353
Net periodic benefit cost (credit), including amount capitalized | (3,010) | (2,161) | (1,721)
Less amount capitalized | 150 | 156 | 113
Net periodic benefit cost (credit) | (3,160) | (2,317) | (1,834)
Other changes in plan assets and benefit obligations recognized in accumulated comprehensive loss: |  |  |
Net (gain) loss | (2,811) | (259) | (127)
Amortization of actuarial loss | (135) | (306) | (110)
Amortization of prior service credit | 100 | 101 | 100
Total recognized in accumulated other comprehensive loss | (2,846) | (464) | (137)
Other changes in plan assets and benefit obligations recognized in regulatory assets or liabilities: |  |  |
Net (gain) loss | (6,292) | (3,793) | (8,168)
Amortization of actuarial gain (loss) | 110 | 19 | (242)
Amortization of prior service credit | 1,298 | 1,297 | 1,297
Total recognized in regulatory assets or liabilities | (4,884) | (2,477) | (7,113)
Total recognized in net periodic benefit cost (credit), accumulated other comprehensive loss and regulatory assets or liabilities | $ (10,890) | $ (5,258) | $ (9,084)

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- Definition Defined Benefit Plan, Amounts Recognized in Regulatory Assets (Liabilities) [Abstract] + References No definition available. + Details
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- Definition The total amount of net periodic benefit cost for defined benefit plans capitalized for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments). + References No definition available. + Details
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- Definition The total amount of net periodic benefit cost including amount capitalized for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments), including amount capitalized. + References No definition available. + Details
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- Definition Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for amortization of actuarial gain (loss) of defined benefit plan. + References No definition available. + Details
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- Definition Amount, before tax, of gain (loss) in other comprehensive income (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit. + References No definition available. + Details
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- Definition Amount, before tax, of reclassification adjustment from accumulated other comprehensive )income) loss for prior service cost (credit) of defined benefit plan. + References No definition available. + Details
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- Definition Amount, before tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit. + References No definition available. + Details
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- Definition Amount, before tax, of reclassification adjustment from regulatory assets or liabilities for prior service cost (credit) of defined benefit plan. + References No definition available. + Details
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123453770&loc=SL108413299-114919 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4587-114921 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920 + Details
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4587-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123453770&loc=SL108413299-114919 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920 + Details
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- Definition Amount of cost recognized for passage of time related to defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123453770&loc=SL108413299-114919 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4587-114921 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920 + Details
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