Accounts Receivable
 12 Months Ended
Dec. 31, 2015
Receivables [Abstract]  
Accounts Receivable
Accounts receivable, net as of December 31, 2015 and 2014 is comprised of the following (in thousands):
 
 
 
December 31,
 
 
2015
 
2014
Trade
 
$
87,744

 
$
150,911

Unbilled revenue
 
23,358

 
72,134

Contract retention
 
25,330

 
43,238

Other receivables
 
17,803

 
3,001

Total accounts receivable
 
154,235

 
269,284

Less: allowance for doubtful accounts
 
(4,482
)
 
(2,723
)
Total accounts receivable, net
 
$
149,753

 
$
266,561


The Company expects all accounts receivable to be collected within one year. The provision for bad debt included in operating expenses in the Consolidated Statements of Operations was $2.9 million, $3.1 million and $1.0 million for the years ended December 31, 2015, 2014 and 2013, respectively.
The balances billed but not paid by customers pursuant to retainage provisions in certain contracts will be due upon completion of the contracts and acceptance by the customer. Based on the Company’s experience with similar contracts within recent years, the majority of the retention balances at each balance sheet date will be collected within the next twelve months.