v3.10.0.1
Employee Benefit Plans (Consolidated Net Periodic Benefit Costs) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Pension Plan [Member]      
Components of net periodic pension and postretirement benefit expense:      
Service cost $ 38,167 $ 20,497 $ 18,179
Interest cost 14,907 9,865 7,950
Expected return on plan assets (12,090) (10,266) (8,913)
Amortization of prior service cost (credit) (181) (181) (181)
Amortization of net actuarial loss 9,763 5,622 4,645
Settlement 1,964 2,460 202
Net periodic expense (credit) 52,530 27,997 21,882
Other Postretirement Benefits [Member]      
Components of net periodic pension and postretirement benefit expense:      
Service cost 243 243 235
Interest cost 416 475 489
Expected return on plan assets 0 0 0
Amortization of prior service cost (credit) 0 0 (3,335)
Amortization of net actuarial loss 589 749 880
Settlement 0 0 0
Net periodic expense (credit) $ 1,248 $ 1,467 $ (1,731)