Retirement Benefit Plans (Components of Net Periodic Benefit Cost) (Details) - Defined Benefit Plan - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost			$ 3	$ 9
Interest cost			624	966
Expected return on plan assets			(956)	(1,384)
Amortization of net loss			324	543
Net periodic benefit cost (credit)	$ 2	$ 45	(5)	134
Hourly Employees’ Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost			0	6
Interest cost			0	300
Expected return on plan assets			0	(486)
Amortization of net loss			0	213
Net periodic benefit cost (credit)			0	33
Employees’ Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost			3	3
Interest cost			624	666
Expected return on plan assets			(956)	(898)
Amortization of net loss			324	330
Net periodic benefit cost (credit)			$ (5)	$ 101