Intangible Assets - Indefinite Lived Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Indefinite-lived Intangible Assets by Major Class [Line Items]
Goodwill	$ 53,593	$ 55,419	$ 9,900
Construction [Member]
Indefinite-lived Intangible Assets by Major Class [Line Items]
Goodwill	28,297	29,190	6,936
Large Project Construction [Member]
Indefinite-lived Intangible Assets by Major Class [Line Items]
Goodwill	23,182	24,115	850
Construction Materials [Member]
Indefinite-lived Intangible Assets by Major Class [Line Items]
Goodwill	$ 2,114	$ 2,114	$ 2,114