Multiemployer Pension Withdrawal (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2013 Location	Jun. 30, 2013 Location	Dec. 31, 2012	Jun. 30, 2012	Jun. 30, 2011
Multiemployer Pension Withdrawal [Abstract]
Number of locations	8	8
Multiemployer pension withdrawal expense (income)			$ 31,683
Total payments			41,186
Annual payment			2,059
Payment term			20 years
Risk free rate (in hundredths)			2.54%
Accretion of present value discount	208	417
Multiemployer pension withdrawal liability	32,100	32,100
Multiemployer pension withdrawal liability (current)	1,244	1,244
Multiemployer pension withdrawal liability (non current)	30,856	30,856
Estimated liability under multiemployer collective bargaining agreements					1,846
Withdrawal settlement amount				$ 43