Retirement Benefit Plans (Schedule of Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 17,858	$ 25,711
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,710	9,686
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,148	16,025
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	680	1,623
Mid Cap | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	680	1,623
Large Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,553	4,411
Large Cap | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,553	4,411
International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,010	2,915
International | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,010	2,915
Liability Driven Solution
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,522	3,543
Liability Driven Solution | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,522	3,543
Wells Fargo BlackRock International Equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	727	1,080
Wells Fargo BlackRock International Equity | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	727	1,080
Wells Fargo Core Bond
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,254	1,774
Wells Fargo Core Bond | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,254	1,774
Wells Fargo/Causeway
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	741	1,112
Wells Fargo/Causeway | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	741	1,112
Wells Fargo BlackRock Large Cap Growth Index Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,009	1,429
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	1,009	1,429
Wells Fargo BlackRock Large Cap Value Index Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,006	1,415
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	1,006	1,415
Wells Fargo Multi-Manager Small Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,189	1,707
Wells Fargo Multi-Manager Small Cap | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,189	1,707
Wells Fargo Russell 2000 Index Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	560	800
Wells Fargo Russell 2000 Index Fund | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	560	800
Wells Fargo S&P Mid Cap Index Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	630	942
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	630	942
Wells Fargo/MFS Value CIT F
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	501	736
Wells Fargo/MFS Value CIT F | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	501	736
Wells Fargo/T. Rowe Price I Large-Cap Growth Managed CIT
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	505	749
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	505	749
T. Rowe Price Equity Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	504	738
T. Rowe Price Equity Income | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	504	738
Cash & Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	467	737
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	$ 467	$ 737