Retirement Benefit Plans (Assumed Health Care Cost Trend Rates) (Details) - Other Post-Retirement Benefits [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Aggregated service and interest cost, 1% Decrease in Rates	$ 666
Postretirement benefit obligation, 1% Decrease in Rates	14,949
Aggregated service and interest cost, Assumed Rates	741
Postretirement benefit obligation, Assumed Rates	16,281
Aggregated service and interest cost, 1% Increase in Rates	834
Postretirement benefit obligation, 1% Increase in Rates	$ 17,894