Summary of Significant Accounting Policies - Goodwill (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Gulf Coast	Dec. 31, 2012 East Coast	Dec. 31, 2008 East Coast	Dec. 31, 2012 Pacific Northwest
Goodwill [Line Items]
Goodwill	$ 34,817	$ 32,168	$ 32,168	$ 22,600			$ 2,600
Goodwill acquired during period	$ 2,649	$ 0				$ 9,600
Revenue growth rate implied in reporting units valuations, number of years projected	5 years
Goodwill impairment test, discount rate applied				18.50%	18.50%
Goodwill impairment test, stabilized growth rate applied	300.00%
Goodwill impairment test, change in discount rate applied				3.25%	1.50%
Reporting unit fair value in excess of carrying value, percent				24.00%	7.00%