Annual report pursuant to Section 13 and 15(d)

Postretirement Benefits, Schedule of Net Periodic Benefits (Details)

v3.6.0.2
Postretirement Benefits, Schedule of Net Periodic Benefits (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Components of net periodic benefit cost:      
Service cost $ 3,806 $ 3,985 $ 3,424
Interest cost 5,637 5,022 4,952
Amortization of prior service credit (51) (51) (51)
Expected return on plan assets (6,997) (6,329) (5,478)
Recognized net actuarial loss 3,278 3,408 2,432
Net periodic benefit cost $ 5,673 $ 6,035 $ 5,279