Retirement Benefit Plans (Schedule of Fair Value of Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 21,838	$ 18,892
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,124	11,789
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10,714	7,103
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Small Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1,321
Small Cap \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1,321
Small Cap \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Small Cap \| 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	1,376	1,238
Mid Cap \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,376	1,238
Large Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,126	7,130
Large Cap \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,126	7,130
International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,201	1,835
International \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,201	1,835
Liability Driven Solution
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,074	2,614
Liability Driven Solution \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Liability Driven Solution \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,074	2,614
Liability Driven Solution \| Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Wells Fargo International Equity Index Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,097	906
Wells Fargo International Equity Index Fund \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,097	906
Wells Fargo Thornburg International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,103
Wells Fargo Thornburg International \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,103
Wells Fargo Large Cap Growth Index Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,216	1,085
Wells Fargo Large Cap Growth Index Fund \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,216	1,085
Wells Fargo Large Cap Value Index Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,210	1,108
Wells Fargo Large Cap Value Index Fund \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,210	1,108
Wells Fargo Multi-Manager Small Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,481
Wells Fargo Multi-Manager Small Cap \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,481
Wells Fargo Russell 2000 Index Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	708	656
Wells Fargo Russell 2000 Index Fund \| Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	708	656
Wells Fargo S&P Mid Cap Index Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	825	734
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	825	734
Cash & Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	421	265
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	$ 421	$ 265

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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