Certain Balance Sheet Components Accounts Receivable, Net, Additional Information (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Current retainage contract receivables [Member]
Long term Retainage Contract Receivables [Line Items]
Contract Receivable Retainage, Next Rolling Twelve Months	$ 4,700,000	$ 3,200,000
Unbilled Contracts Receivable	4,000,000	4,300,000
Long Term Retainage Contract Receivables [Member]
Long term Retainage Contract Receivables [Line Items]
Unbilled Receivables, Not Billable, Amount Expected to be Collected after Next Twelve Months	4,300,000	4,700,000
Contract Receivable Retainage, Due after Next Rolling Twelve Months	$ 0	$ 0