Labor Union Contracts (Details)	0 Months Ended	6 Months Ended
	Jul. 30, 2013 Employee	Jun. 30, 2013
Labor Union Contracts
Percentage of employees who are members of bargaining units		38.00%
Employees covered under collective bargaining agreements
Labor Union Contracts
Number of employees covered under the agreement	12,000
Minimum advance notice period		24 hours
Period of labor contract	4 years
Collective bargaining agreements that expired on October 6, 2012
Labor Union Contracts
Percentage of concentration risk		26.00%
Number of employees covered under the agreement		12,000
Collective bargaining agreements that expired after October 6, 2012
Labor Union Contracts
Percentage of concentration risk		3.00%
Number of employees covered under the agreement		1,500