Multiemployer Pension Withdrawal (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2011
Multiemployer Pension Withdrawal [Abstract]
Multiemployer pension withdrawal liability	$ 0			$ 0		$ 1,846
Payments against multiemployer pension withdrawal liability	1,600	43		1,643
Multiemployer pension withdrawal expense (income)	$ (203)		$ 0	$ (203)	$ 1,846