Retirement Benefit Plans (Schedule of Net Periodic Benefit Cost) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 14	$ 12
Interest cost	1,199	1,327
Expected return on plan assets	(1,471)	(1,477)
Amortization of prior service cost	0	0
Amortization of net (gain)/loss	659	194
Net periodic benefit cost	401	56
Supplemental Employee Retirement Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	101	108
Interest cost	104	103
Amortization of prior service cost	287	264
Net periodic benefit cost	492	475
Hourly Employees’ Pension Plan | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	10	8
Interest cost	411	469
Expected return on plan assets	(520)	(514)
Amortization of prior service cost	0	0
Amortization of net (gain)/loss	280	117
Net periodic benefit cost	181	80
Employees’ Retirement Plan | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	4
Interest cost	788	858
Expected return on plan assets	(951)	(963)
Amortization of prior service cost	0	0
Amortization of net (gain)/loss	379	77
Net periodic benefit cost	$ 220	$ (24)