Acquisition Acquired Intangibles Amortiation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Acquired Indefinite-lived Intangible Assets [Line Items]
Amortization expense	$ 2,200	$ 1,200	$ 6,700	$ 3,300
Kenny [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Amortization expense	1,880		5,691
Cost of Revenue | Large Project Construction [Member] | Kenny [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Amortization expense	99		347
Cost of Revenue | Construction [Member] | Kenny [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Amortization expense	1,600		4,800
Selling, General and Administrative Expenses | Kenny [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Amortization expense	$ 181		$ 544