Labor Union Contracts (Details)		9 Months Ended		0 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 Collective bargaining agreements that expired on October 6, 2012 Employee	Sep. 30, 2013 Collective bargaining agreements that expired after October 6, 2012 Employee	Jul. 30, 2013 Employees covered under collective bargaining agreements Employee
Labor Union Contracts
Percentage of employees who are members of bargaining units (as a percent)	37.00%
Number of employees covered under the agreement (employees)		12,000	1,600	12,000
Percentage of concentration risk (as a percent)		26.00%	4.00%
Period of labor contract				4 years