Pension Plans and Postretirement Benefits (Narrative) (Details) $ in Millions	2 Months Ended	3 Months Ended	12 Months Ended
	Feb. 24, 2017	Mar. 29, 2015 USD ($)	Dec. 31, 2017	Jan. 01, 2017 USD ($) insurancecompany participant	Jan. 03, 2016 USD ($)	Dec. 28, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Pension expense (income)				$ (3.0)	$ 2.0	$ 1.7
One-time related to frozen non-qualified pension plan for top executives		$ 1.2
Amount recoverable from government contract due to US government cost accounting standards				$ 13.8	13.8	13.8
Number of insurance companies | insurancecompany				2
Annuity premium				$ 27.2
Pension plan participants | participant				1,193
Employer contributions to 401(k) plans				$ 9.3	10.1	9.5
Non-cash reduction to stockholders' equity				249.6	232.3
Deferred tax on non-cash reductions to stockholders' equity				$ 147.3	138.0
Assumed rate of increase in the per capita cost of covered benefits 2017				6.50%
Assumed rate of decrease in the per capita cost of covered benefits by 2023				5.00%
Effect of one percentage point increase in assumed health care cost trend rates on annual service and interest costs (less than)				$ 0.1
Effect of one percentage point increase in assumed health care cost trend rates on postretirement benefit obligation				0.3
Effect of one percentage point decrease in assumed health care cost trend rates on annual service and interest costs				0.1
Effect of one percentage point decrease in assumed health care cost trend rates on postretirement benefit obligation				0.3
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Minimum liability adjustment to be recognized for the pension plans, net gain (loss)				29.2
Minimum liability adjustment to be recognized for the pension plans, net prior service credit				6.1
Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Pension expense (income)				0.1	0.3	(0.1)
Minimum liability adjustment to be recognized for the pension plans, net gain (loss)				0.4
Minimum liability adjustment to be recognized for the pension plans, net prior service credit				0.1
Unrecognized net gain				(3.8)	(4.2)
Unrecognized prior service credit				$ 0.1
Domestic
Defined Benefit Plan Disclosure [Line Items]
Percentage of employees under defined benefit pension plan				16.00%
Pension expense (income)				$ (3.0)	2.0	(1.7)
One-time related to frozen non-qualified pension plan for top executives				0.0	(1.2)	$ 0.0
Settlements				$ 14.6	$ 10.5
Expected long-term rate of return				8.00%	8.25%	8.25%
Unrecognized net gain				$ 421.5	$ 398.6
Unrecognized prior service credit				$ 30.7	36.7
Domestic | Equity instruments
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets				70.00%
Target allocation of plan assets, minimum				45.00%
Target allocation of plan assets, maximum				75.00%
Domestic | Fixed income instruments
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets				30.00%
Domestic | Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return			8.00%
Foreign
Defined Benefit Plan Disclosure [Line Items]
Pension expense (income)				$ 0.8	1.0	$ 0.4
One-time related to frozen non-qualified pension plan for top executives				0.0	0.0	$ 0.0
Unrecognized net gain				10.3	13.0
Unrecognized prior service credit				$ 0.5	$ 0.3
Foreign | Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return				1.40%	1.80%	3.00%
Foreign | Minimum | Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return	1.00%
Foreign | Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return				6.50%	6.40%	6.40%
Foreign | Maximum | Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return	5.90%