Goodwill and Intangible Assets (Details 3) (USD $)	3 Months Ended			3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013 Trade Names (Amortizable)	Dec. 31, 2012 Trade Names (Amortizable)	Mar. 31, 2013 Customer relationships	Dec. 31, 2012 Customer relationships	Mar. 31, 2013 Construction contract backlog	Dec. 31, 2012 Construction contract backlog
Finite-Lived intangible assets
Cost				$ 74,350,000	$ 74,350,000	$ 39,800,000	$ 39,800,000	$ 73,706,000	$ 73,706,000
Accumulated amortization				(4,475,000)	(3,854,000)	(13,351,000)	(13,029,000)	(57,012,000)	(54,685,000)
Accumulated impairment charge				(23,232,000)	(23,232,000)	(16,645,000)	(16,645,000)
Carrying value				46,643,000	47,264,000	9,804,000	10,126,000	16,694,000	19,021,000
Weighted average amortization period				20 years	20 years	11 years 4 months 24 days	11 years 4 months 24 days	3 years 7 months 6 days	3 years 7 months 6 days
Total intangible assets
Cost	311,456,000		311,456,000
Accumulated amortization	(74,838,000)		(71,568,000)
Accumulated impairment charge	(113,067,000)		(113,067,000)
Carrying value	123,551,000		126,821,000
Amortization expense
Amortization expense	3,300,000	5,000,000
Remainder of 2013	9,800,000
Amortization expense, 2014	11,900,000
Amortization expense, 2015	5,300,000
Amortization expense, 2016	3,500,000
Amortization expense, 2017	3,500,000
Amortization expense, thereafter	$ 39,100,000