Retirement Benefit Plans (Schedule of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 13	$ 12
Interest cost	1,273	1,274
Expected return on plan assets	(1,890)	(1,817)
Amortization of net loss (gain)	649	132
Net periodic benefit cost	45	(399)
Supplemental Employee Retirement Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	121	152
Interest cost	137	138
Amortization of prior service cost	342	270
Net periodic benefit cost	600	560
Hourly Employees’ Pension Plan | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	9	8
Interest cost	405	422
Expected return on plan assets	(661)	(637)
Amortization of net loss (gain)	248	72
Net periodic benefit cost	1	(135)
Employees’ Retirement Plan | Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	4
Interest cost	868	852
Expected return on plan assets	(1,229)	(1,180)
Amortization of net loss (gain)	401	60
Net periodic benefit cost	$ 44	$ (264)