Retirement Benefit Plans (Changes in Fair Value of Level 3 Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance	$ 161,369
Ending balance	192,734	$ 161,369
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance	934	1,077
Unrealized gains relating to instruments still held at the reporting date	(10)	(28)
Benefit payments, administrative expenses, and interest income, net	(131)	(115)
Ending balance	$ 793	$ 934