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