Goodwill and Intangible Assets - Future Amortization Expense of Finite-lived Intangible Assets (Details) (West Construction, Inc., USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2013	419
2014	111
2015	97
Minimum
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Acquired intangible assets useful life	1 year
Maximum
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Acquired intangible assets useful life	3 years