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Retirement Benefit Plans (Schedule of Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | $ 18,106 | $ 20,327
Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 6,203 | 7,007
Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 11,903 | 13,320
Significant Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Mid Cap |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,176 | 1,321
Mid Cap | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,176 | 1,321
Large Cap |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 2,618 | 2,930
Large Cap | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 2,618 | 2,930
International |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 2,051 | 2,300
International | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 2,051 | 2,300
Liability Driven Solution |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 2,532 | 2,845
Liability Driven Solution | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 2,532 | 2,845
Wells Fargo BlackRock International Equity |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 765 | 859
Wells Fargo BlackRock International Equity | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 765 | 859
Wells Fargo Core Bond |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,266 | 1,416
Wells Fargo Core Bond | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,266 | 1,416
Wells Fargo/Causeway |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 766 | 861
Wells Fargo/Causeway | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 766 | 861
Wells Fargo BlackRock Large Cap Growth Index Fund |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,026 | 1,146
Wells Fargo BlackRock Large Cap Growth Index Fund | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,026 | 1,146
Wells Fargo BlackRock Large Cap Value Index Fund |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,025 | 1,146
Wells Fargo BlackRock Large Cap Value Index Fund | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,025 | 1,146
Wells Fargo Multi-Manager Small Cap |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,246 | 1,387
Wells Fargo Multi-Manager Small Cap | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,246 | 1,387
Wells Fargo Russell 2000 Index Fund |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 573 | 636
Wells Fargo Russell 2000 Index Fund | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 573 | 636
Wells Fargo S&P Mid Cap Index Fund |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 641 | 715
Wells Fargo S&P Mid Cap Index Fund | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 641 | 715
Wells Fargo/MFS Value CIT F |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 516 | 578
Wells Fargo/MFS Value CIT F | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 516 | 578
Wells Fargo/T. Rowe Price I Large-Cap Growth Managed CIT |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 516 | 577
Wells Fargo/T. Rowe Price I Large-Cap Growth Managed CIT | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 516 | 577
Wells Fargo/T. Rowe Price Equity Income |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 515 | 577
Wells Fargo/T. Rowe Price Equity Income | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 515 | 577
Wells Fargo Voya Large Cap Growth CIT F |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 516 | 577
Wells Fargo Voya Large Cap Growth CIT F | Significant Other Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 516 | 577
Cash & Short-term Investments |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 358 | 456
Cash & Short-term Investments | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | $ 358 | $ 456

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