XML 81 R64.htm IDEA: XBRL DOCUMENT v3.10.0.1
Components of Retirement Plan Costs (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Service Cost $ 3,393 $ 3,295 $ 3,402
Interest Cost 5,878 6,057 5,945
Expected Return on Plan Assets (7,785) (7,306) (7,257)
Prior Service Cost Amortization 324 263 263
Actuarial Loss Amortization 5,786 4,662 4,398
Sub-total 7,596 6,971 6,751
Amounts Capitalized or Deferred (3,465) (3,122) (3,008)
NPBC Recognized 4,131 3,849 3,743
Other Postretirement Benefit Plans, Defined Benefit      
Defined Benefit Plan Disclosure [Line Items]      
Service Cost 2,933 2,974 2,610
Interest Cost 3,404 3,913 3,232
Expected Return on Plan Assets (1,635) (1,347) (1,205)
Prior Service Cost Amortization 1,309 1,399 1,486
Actuarial Loss Amortization 1,383 2,098 1,049
Sub-total 7,394 9,037 7,172
Amounts Capitalized or Deferred (3,416) (4,515) (3,351)
NPBC Recognized 3,978 4,522 3,821
Supplemental Employee Retirement Plans, Defined Benefit      
Defined Benefit Plan Disclosure [Line Items]      
Service Cost 487 460 162
Interest Cost 404 392 386
Prior Service Cost Amortization 189 189 189
Actuarial Loss Amortization 486 295 375
Sub-total 1,566 1,336 1,112
Amounts Capitalized or Deferred (451) (397) (290)
NPBC Recognized $ 1,115 $ 939 $ 822