Pension Plans, Reconciliation of Assets Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Details) - Noncontributory Defined-Benefit Pension Plan [Member] - USD ($)
$ in Thousands |
12 Months Ended |
Dec. 31, 2016 |
Dec. 31, 2015 |
| Summary of reconciliation of the beginning and ending balances of assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) [Abstract] |
|
|
| Fair value of plan assets at beginning of year |
$ 130,061
|
$ 128,108
|
| Actual return on program assets [Abstract] |
|
|
| Fair value of plan assets at end of year |
140,398
|
130,061
|
| Level 3 [Member] |
|
|
| Summary of reconciliation of the beginning and ending balances of assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) [Abstract] |
|
|
| Fair value of plan assets at beginning of year |
6,496
|
7,294
|
| Actual return on program assets [Abstract] |
|
|
| Relating to assets still held at the reporting date |
520
|
487
|
| Relating to assets sold during the period |
73
|
597
|
| Purchases, issuances, and settlements |
669
|
(1,882)
|
| Transfer in and/or out |
(209)
|
0
|
| Fair value of plan assets at end of year |
7,549
|
6,496
|
| Government Obligations [Member] | Level 3 [Member] |
|
|
| Summary of reconciliation of the beginning and ending balances of assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) [Abstract] |
|
|
| Fair value of plan assets at beginning of year |
0
|
0
|
| Actual return on program assets [Abstract] |
|
|
| Relating to assets still held at the reporting date |
0
|
0
|
| Relating to assets sold during the period |
0
|
0
|
| Purchases, issuances, and settlements |
0
|
0
|
| Transfer in and/or out |
0
|
0
|
| Fair value of plan assets at end of year |
0
|
0
|
| Corporate Obligations [Member] | Level 3 [Member] |
|
|
| Summary of reconciliation of the beginning and ending balances of assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) [Abstract] |
|
|
| Fair value of plan assets at beginning of year |
0
|
0
|
| Actual return on program assets [Abstract] |
|
|
| Relating to assets still held at the reporting date |
0
|
0
|
| Relating to assets sold during the period |
0
|
0
|
| Purchases, issuances, and settlements |
0
|
0
|
| Transfer in and/or out |
0
|
0
|
| Fair value of plan assets at end of year |
0
|
0
|
| Partnership/Joint venture [Member] | Level 3 [Member] |
|
|
| Summary of reconciliation of the beginning and ending balances of assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) [Abstract] |
|
|
| Fair value of plan assets at beginning of year |
567
|
1,097
|
| Actual return on program assets [Abstract] |
|
|
| Relating to assets still held at the reporting date |
19
|
103
|
| Relating to assets sold during the period |
1
|
(39)
|
| Purchases, issuances, and settlements |
345
|
(594)
|
| Transfer in and/or out |
0
|
0
|
| Fair value of plan assets at end of year |
932
|
567
|
| Real Estate [Member] | Level 3 [Member] |
|
|
| Summary of reconciliation of the beginning and ending balances of assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) [Abstract] |
|
|
| Fair value of plan assets at beginning of year |
5,929
|
6,197
|
| Actual return on program assets [Abstract] |
|
|
| Relating to assets still held at the reporting date |
501
|
384
|
| Relating to assets sold during the period |
72
|
636
|
| Purchases, issuances, and settlements |
324
|
(1,288)
|
| Transfer in and/or out |
(209)
|
0
|
| Fair value of plan assets at end of year |
6,617
|
5,929
|
| Hedge Funds [Member] | Level 3 [Member] |
|
|
| Summary of reconciliation of the beginning and ending balances of assets measured at fair value on a recurring basis using significant unobservable inputs (Level 3) [Abstract] |
|
|
| Fair value of plan assets at beginning of year |
0
|
0
|
| Actual return on program assets [Abstract] |
|
|
| Relating to assets still held at the reporting date |
0
|
0
|
| Relating to assets sold during the period |
0
|
0
|
| Purchases, issuances, and settlements |
0
|
0
|
| Transfer in and/or out |
0
|
0
|
| Fair value of plan assets at end of year |
$ 0
|
$ 0
|