XML 77 R51.htm IDEA: XBRL DOCUMENT v3.2.0.727
Retirement Plans and Other Post-Retirement Benefits - Schedule of Net Periodic Costs of Pension and Post Retirement Medical Benefit Plans (Detail) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Pension Benefits [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 2,561 $ 2,504 $ 5,696 $ 5,208
Interest cost 5,788 6,309 11,738 12,480
Expected return on plan assets (11,454) (10,931) (22,997) (21,938)
Amortization of prior service cost 761 921 1,521 1,655
Amortization of unrecognized loss 3,947 3,014 8,453 5,954
Net periodic benefit cost 1,603 1,817 4,411 3,359
Other Benefits [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 303 615 716 1,230
Interest cost 436 598 999 1,196
Amortization of prior service cost (70) (72) (140) (144)
Amortization of unrecognized loss 15 129 115 258
Net periodic benefit cost $ 684 $ 1,270 $ 1,690 $ 2,540