Retirement Plans - Weighted-average assumptions (Details)	12 Months Ended
	Dec. 31, 2016	Jan. 02, 2016	Jan. 03, 2015
Pension Benefits
Net periodic benefit cost
Discount rate (as a percent)	4.66%	4.25%	4.92%
Expected long-term rate of return on assets (as a percent)	7.58%	7.57%	7.60%
Rate of compensation increase (as a percent)	3.49%	3.49%	3.50%
Benefit obligations at year-end
Discount rate (as a percent)	4.13%	4.66%	4.18%
Rate of compensation increase (as a percent)	3.50%	3.49%	3.49%
Postretirement Benefits Other Than Pensions
Net periodic benefit cost
Discount rate (as a percent)	4.50%	4.00%	4.50%
Benefit obligations at year-end
Discount rate (as a percent)	4.00%	4.50%	4.00%