Acquisition Acquired Intangibles Amortiation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Acquired Indefinite-lived Intangible Assets [Line Items]
Amortization expense	$ 2,300	$ 1,000	$ 4,500	$ 2,100
Kenny [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Amortization expense	181		362
Large Project Construction [Member] | Kenny [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Amortization expense	140		247
Construction [Member] | Kenny [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Amortization expense	$ 1,600		$ 3,200