Employee Benefit Plan - Net Periodic Benefit Cost (Details) - USD ($)
$ in Thousands |
12 Months Ended |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
| DB Pension Plan |
|
|
|
| Components of net periodic benefit cost |
|
|
|
| Service cost |
$ 0
|
$ 0
|
$ 1,587
|
| Interest cost |
2,501
|
2,473
|
2,987
|
| Expected return on plan assets |
(5,088)
|
(4,844)
|
(5,028)
|
| Amortization of prior service (credit) cost |
(10)
|
(15)
|
(448)
|
| Recognized net actuarial loss |
1,075
|
975
|
1,573
|
| Recognized net actuarial gain due to curtailments |
0
|
0
|
(6,003)
|
| Net periodic benefit (credit) cost |
(1,522)
|
(1,411)
|
(5,332)
|
| Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss) |
|
|
|
| Net actuarial loss (gain) |
1,434
|
1,880
|
(169)
|
| Recognized actuarial loss |
(1,075)
|
(975)
|
(1,573)
|
| Prior service (credit) cost |
0
|
0
|
0
|
| Recognized prior service cost (credit) |
10
|
15
|
6,451
|
| Recognized in other comprehensive income (loss) |
369
|
920
|
4,709
|
| Total recognized in net periodic benefit cost and other comprehensive income (loss) |
(1,153)
|
(491)
|
(623)
|
| Life and Healthcare Plan |
|
|
|
| Components of net periodic benefit cost |
|
|
|
| Service cost |
192
|
258
|
236
|
| Interest cost |
268
|
283
|
323
|
| Expected return on plan assets |
0
|
0
|
0
|
| Amortization of prior service (credit) cost |
(62)
|
16
|
16
|
| Recognized net actuarial loss |
34
|
5
|
19
|
| Recognized net actuarial gain due to curtailments |
0
|
0
|
0
|
| Net periodic benefit (credit) cost |
432
|
562
|
594
|
| Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss) |
|
|
|
| Net actuarial loss (gain) |
708
|
210
|
(467)
|
| Recognized actuarial loss |
(34)
|
(5)
|
(19)
|
| Prior service (credit) cost |
(964)
|
0
|
0
|
| Recognized prior service cost (credit) |
62
|
(16)
|
(16)
|
| Recognized in other comprehensive income (loss) |
(228)
|
189
|
(502)
|
| Total recognized in net periodic benefit cost and other comprehensive income (loss) |
204
|
751
|
92
|
| SERPs |
|
|
|
| Components of net periodic benefit cost |
|
|
|
| Service cost |
166
|
171
|
201
|
| Interest cost |
852
|
832
|
928
|
| Expected return on plan assets |
0
|
0
|
0
|
| Amortization of prior service (credit) cost |
87
|
75
|
73
|
| Recognized net actuarial loss |
399
|
358
|
626
|
| Recognized net actuarial gain due to curtailments |
0
|
0
|
0
|
| Net periodic benefit (credit) cost |
1,504
|
1,436
|
1,828
|
| Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss) |
|
|
|
| Net actuarial loss (gain) |
2,407
|
697
|
(1,210)
|
| Recognized actuarial loss |
(399)
|
(358)
|
(626)
|
| Prior service (credit) cost |
0
|
188
|
0
|
| Recognized prior service cost (credit) |
(87)
|
(75)
|
(73)
|
| Recognized in other comprehensive income (loss) |
1,921
|
452
|
(1,909)
|
| Total recognized in net periodic benefit cost and other comprehensive income (loss) |
$ 3,425
|
$ 1,888
|
$ (81)
|