Labor Union Contracts (Details) (Employees covered under collective bargaining agreements)	12 Months Ended
	Dec. 31, 2013 Employee
Employees covered under collective bargaining agreements
Labor Union Contracts
Approximate percentage of employees who are members of bargaining units (as a percent)	53.00%
Collective bargaining agreements, term	4 years
Collective Bargaining Arrangement, Number of Participating Employees	12,000