XML 68 R51.htm IDEA: XBRL DOCUMENT v3.8.0.1
Employee Benefit Plans - Summary of Components of Net Periodic Benefit Cost and Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Other changes in plan assets and benefit obligations recognized in other comprehensive income:      
Tax expense related to benefit plans included in other comprehensive income $ 4,500 $ 1,200 $ 1,100
Postretirement benefit plans      
Net periodic benefit cost:      
Service cost 4,045 5,557 6,105
Interest cost 17,961 24,526 26,007
Expected return on plan assets (23,072) (25,726) (29,850)
Amortization of prior service cost (credit) 29 461 (465)
Recognized actuarial loss 8,362 6,994 15,168
Settlement loss 0 1,772 6,453
Curtailment loss (gain) 103 415 (8,639)
Net periodic benefit cost 7,428 13,999 14,779
Other changes in plan assets and benefit obligations recognized in other comprehensive income:      
Net actuarial loss (gain) 46 (1,531) (8,813)
Prior service cost (credit) 0 505 8,691
Amortization of prior service (cost) credit (29) (461) 465
Total recognized in other comprehensive income (loss) 17 (1,487) 343
Total recognized in net periodic benefit cost and other comprehensive income (loss) 7,445 12,512 15,122
Deferred compensation and excess benefit plans      
Net periodic benefit cost:      
Service cost 2 52 54
Interest cost 812 1,143 1,194
Expected return on plan assets 0 0 0
Amortization of prior service cost (credit) 0 0 0
Recognized actuarial loss 149 148 148
Settlement loss 0 0 0
Curtailment loss (gain) 0 0 0
Net periodic benefit cost 963 1,343 1,396
Other changes in plan assets and benefit obligations recognized in other comprehensive income:      
Net actuarial loss (gain) (2,746) (1,833) (3,130)
Prior service cost (credit) (16,261) 0 0
Amortization of prior service (cost) credit 0 0 0
Total recognized in other comprehensive income (loss) (19,007) (1,833) (3,130)
Total recognized in net periodic benefit cost and other comprehensive income (loss) $ (18,044) $ (490) $ (1,734)