Labor Union Contracts (Details)	12 Months Ended
	Dec. 31, 2015 Employee
Employees subject to collective bargaining arrangements that have expired
Labor Union Contracts
Number of unionized employees	300
Employees subject to collective bargaining arrangements expiring within one year
Labor Union Contracts
Number of unionized employees	1,000
Total number of employees | Unionized employees concentration risk
Labor Union Contracts
Concentration risk (percent)	37.00%
Total number of employees | Unionized employees concentration risk | Employees subject to collective bargaining arrangements that have expired
Labor Union Contracts
Concentration risk (percent)	2.00%
Total number of employees | Unionized employees concentration risk | Employees subject to collective bargaining arrangements expiring within one year
Labor Union Contracts
Concentration risk (percent)	6.00%