Retirement Benefit Plans (Components of Net Periodic Benefit Cost) (Details) - Defined Benefit Plan - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 3
Interest cost	208	322
Expected return on plan assets	(319)	(461)
Amortization of net loss	108	181
Net periodic benefit cost (credit)	(2)	45
Hourly Employees’ Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	2
Interest cost	0	100
Expected return on plan assets	0	(162)
Amortization of net loss	0	71
Net periodic benefit cost (credit)	0	11
Employees’ Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	208	222
Expected return on plan assets	(319)	(299)
Amortization of net loss	108	110
Net periodic benefit cost (credit)	$ (2)	$ 34