Quarterly report pursuant to Section 13 or 15(d)

Postretirement Benefits (Details)

v3.7.0.1
Postretirement Benefits (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Components of net periodic benefit cost:    
Service cost $ 976 $ 952
Interest cost 1,395 1,409
Expected return on plan assets (1,549) (1,749)
Amortization of net loss 775 806
Net periodic benefit cost $ 1,597 $ 1,418