Pension Plans and Postretirement Benefits (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Estimated contributions in current fiscal year	$ 0		$ 0
Pension Benefits Allocated to Contracts Pursuant to U.S. Government Cost Accounting Standards
Defined Benefit Plan Disclosure [Line Items]
Pension expense allocated to contracts pursuant to U.S. Government Cost Accounting Standards	$ 3,200,000	$ 3,500,000	$ 9,700,000	$ 10,400,000
United States
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to determine the benefit obligation	4.02%		4.02%		4.54%