Pension Plans and Postretirement Benefits (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Oct. 01, 2017	Oct. 02, 2016	Jan. 01, 2017
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer by during period			$ 0	$ 0
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	$ 3,500,000	$ 3,400,000	$ 10,400,000	$ 10,400,000
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to determine the benefit obligation	4.54%		4.54%		4.91%