XML 76 R59.htm IDEA: XBRL DOCUMENT v3.8.0.1
Benefit Plans Net Periodic Benefit Cost (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Pension Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost $ 4,699 $ 4,447 $ 5,072
Interest cost 6,993 6,830 6,342
Expected return on assets (7,888) (7,288) (6,984)
Amortization of prior service cost 94 376 376
Recognized actuarial loss 3,844 3,527 4,005
Net periodic pension cost 7,742 7,892 8,811
Other Postretirement Benefits Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 529 527 379
Interest cost 634 655 504
Expected return on assets (376) (292) (283)
Amortization of prior service cost 198 197 197
Recognized actuarial loss 273 316 188
Net periodic pension cost $ 1,258 $ 1,403 $ 985