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Components of Retirement Plan Costs (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Pension Plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service Cost | $ 3,472 | $ 3,322 | $ 3,104
Interest Cost | 5,003 | 5,776 | 6,484
Expected Return on Plan Assets | (9,693) | (9,019) | (8,475)
Prior Service Cost Amortization | 301 | 320 | 320
Actuarial Loss Amortization | 8,089 | 6,472 | 4,324
Sub-total | 7,172 | 6,871 | 5,757
Amounts Capitalized or Deferred | (3,384) | (3,083) | (2,227)
NPBC Recognized | 3,788 | 3,788 | 3,530
Other Postretirement Benefit Plans, Defined Benefit |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service Cost | 3,034 | 2,698 | 2,304
Interest Cost | 2,740 | 3,121 | 3,426
Expected Return on Plan Assets | (2,508) | (2,063) | (1,645)
Prior Service Cost Amortization | 1,208 | 1,210 | 1,213
Actuarial Loss Amortization | 1,045 | 744 | 227
Sub-total | 5,519 | 5,710 | 5,525
Amounts Capitalized or Deferred | (3,136) | (2,865) | (2,317)
NPBC Recognized | 2,383 | 2,845 | 3,208
Supplemental Employee Retirement Plans, Defined Benefit |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service Cost | 354 | 283 | 247
Interest Cost | 458 | 549 | 567
Prior Service Cost Amortization | 56 | 57 | 56
Actuarial Loss Amortization | 1,489 | 1,036 | 628
Sub-total | 2,357 | 1,925 | 1,498
Amounts Capitalized or Deferred | (712) | (579) | (430)
NPBC Recognized | $ 1,645 | $ 1,346 | $ 1,068

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