Multipemployer Pension and Postretirement Plans Multiemployer Pension Plans Trusts Funds (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Multiemployer Plans [Line Items]
Multiemployer Plan, Period Contributions		$ 15.9	$ 13.7	$ 14.7
Bakery And Confectionary Union And Industry International Pension Fund [Member]
Multiemployer Plans [Line Items]
Multiemployer Plans, Collective-Bargaining Arrangement, Percentage of Employer's Participants		80.00%
Entity Tax Identification Number	[1]	526118572
Multiemployer Plan Number	[1]	001
Multiemployer Plans, Certified Zone Status	[1]	Red	Red
Multiemployer Plans, Certified Zone Status, Date	[1]	Dec. 31, 2017	Dec. 31, 2016
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date, First	[1]	Dec. 17, 2019
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date, Last	[1]	Mar. 16, 2021
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date	[1],[2]	Mar. 16, 2021
Multiemployer Plans, Funding Improvement Plan and Rehabilitation Plan	[1]	Implemented
Multiemployer Plan, Period Contributions	[1]	$ 6.6	$ 4.8	5.1
Multiemployer Plans, Surcharge	[1]	Yes
Central States Southeast And Southwest Areas Pension Fund [Member]
Multiemployer Plans [Line Items]
Entity Tax Identification Number		366044243
Multiemployer Plan Number		001
Multiemployer Plans, Certified Zone Status		Red	Red
Multiemployer Plans, Certified Zone Status, Date		Dec. 31, 2017	Dec. 31, 2016
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date, First
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date, Last
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date	[2]	Jul. 29, 2018
Multiemployer Plans, Funding Improvement Plan and Rehabilitation Plan		Implemented
Multiemployer Plan, Period Contributions		$ 4.8	$ 4.8	4.8
Multiemployer Plans, Surcharge		Yes
Western Conference Of Teamsters Pension Trust [Member]
Multiemployer Plans [Line Items]
Entity Tax Identification Number		916145047
Multiemployer Plan Number		001
Multiemployer Plans, Certified Zone Status		Green	Green
Multiemployer Plans, Certified Zone Status, Date		Dec. 31, 2017	Dec. 31, 2016
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date, First
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date, Last
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date	[3]	Mar. 24, 2018
Multiemployer Plans, Funding Improvement Plan and Rehabilitation Plan		NA
Multiemployer Plan, Period Contributions		$ 1.4	$ 1.0	1.6
Multiemployer Plans, Surcharge		No
Hagerstown Motor Carriers And Teamsters Pension Fund [Member]
Multiemployer Plans [Line Items]
Entity Tax Identification Number		526045424
Multiemployer Plan Number		001
Multiemployer Plans, Certified Zone Status		Red	Red
Multiemployer Plans, Certified Zone Status, Date		Jun. 30, 2018	Jun. 30, 2017
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date	[4]
Multiemployer Plans, Funding Improvement Plan and Rehabilitation Plan		Implemented
Multiemployer Plan, Period Contributions		$ 0.4	$ 0.6	0.5
Multiemployer Plans, Surcharge		No
Local 734 Pension Plan [Member]
Multiemployer Plans [Line Items]
Entity Tax Identification Number		516040136
Multiemployer Plan Number		001
Multiemployer Plans, Certified Zone Status		Red	Red
Multiemployer Plans, Certified Zone Status, Date		Apr. 30, 2018	Apr. 30, 2017
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date	[4]
Multiemployer Plans, Funding Improvement Plan and Rehabilitation Plan		Implemented
Multiemployer Plan, Period Contributions		$ 0.2	$ 0.2	0.3
Multiemployer Plans, Surcharge		Yes
Twin Cities Bakery Drivers Pension Plan [Member]
Multiemployer Plans [Line Items]
Entity Tax Identification Number		416172265
Multiemployer Plan Number		001
Multiemployer Plans, Certified Zone Status		Green	Green
Multiemployer Plans, Certified Zone Status, Date		Dec. 31, 2017	Dec. 31, 2016
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date	[4]
Multiemployer Plans, Funding Improvement Plan and Rehabilitation Plan		NA
Multiemployer Plan, Period Contributions		$ 0.2	$ 0.2	0.2
Multiemployer Plans, Surcharge		Yes
Upstate New York Bakery Drivers And Industry Pension Fund [Member]
Multiemployer Plans [Line Items]
Entity Tax Identification Number		150612437
Multiemployer Plan Number		001
Multiemployer Plans, Certified Zone Status		Green	Green
Multiemployer Plans, Certified Zone Status, Date		Jun. 30, 2017	Jun. 30, 2016
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date	[4]
Multiemployer Plans, Funding Improvement Plan and Rehabilitation Plan		NA
Multiemployer Plan, Period Contributions		$ 0.1	$ 0.0	0.2
Multiemployer Plans, Surcharge		No
Other Plans [Member]
Multiemployer Plans [Line Items]
Multiemployer Plans, Collective-Bargaining Arrangement, Expiration Date	[5]
Multiemployer Plan, Period Contributions		$ 2.2	$ 2.1	$ 2.0

[1] The Company is party to multiple CBAs requiring contributions to this fund, each with its own expiration date. Over 80 percent of the Company’s participants in this fund are covered by a single CBA that expires on 3/16/2021.

[2] During 2017, the Company terminated certain CBAs covered by these funds. Because of the Company's level of continuing involvement in each fund, the Company does not anticipate being subject to a withdrawal liability. The Company does not expect a material change in contributions for 2018.

[3] During 2017, the Company terminated certain CBAs covered by this fund. As a result, the Company has partially withdrawn from the fund and recognized expense for its estimated withdrawal liability. The Company does not expect a material change in contributions for 2018.

[4] During 2017, the Company terminated the CBAs, and withdrew from the funds. As a result, the Company recognized expense for the estimated withdrawal liability and will make no contributions in 2018.

[5] During 2017, the Company terminated the CBAs covered by certain of these funds. As a result, for the impacted funds, the Company recognized expense for the estimated withdrawal liability and will make no contributions in 2018.