Retirement Benefits Plans (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2011	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Company's pretax income and the aggregate compensation levels of participating employees		$ 6.8	$ 6.5	$ 6.4
Postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Years of service, less than	10 years
Health care cost trend assumption increased health care cost trend rates (as a percent)		6.50%	6.50%
Health care cost trend assumption increased health care cost trend rates (as a percent)		5.00%