Contract cost and recognized income not yet billed on uncompleted contracts arise when recorded revenues for a contract exceed the amounts billed under the terms of the contracts. Contract billings in excess of cost and recognized income arise when billed amounts exceed revenues recorded. Amounts are billable to customers upon various measures of performance, including achievement of certain milestones, completion of specified units, or completion of the contract. Also included in contract cost and recognized income not yet billed on uncompleted contracts are amounts the Company seeks to collect from customers for change orders approved in scope but not for price associated with that scope change (unapproved change orders). Revenue for these amounts is recorded equal to the lesser of the expected revenue or cost incurred when realization of price approval is probable. Estimating revenues from unapproved change orders involves the use of estimates, and it is reasonably possible that revisions to the estimated recoverable amounts of recorded unapproved change orders may be made in the near-term. If the Company does not successfully resolve these matters, a reduction in revenues may be required to amounts that have been previously recorded.

Contract cost and recognized income not yet billed and related amounts billed as of March 31, 2016 and December 31, 2015 was as follows (in thousands):



	March 31, 2016			December 31, 2015
Cost incurred on contracts in progress	$	454,133		$	567,144
Recognized income	15,232			50,812
	469,365			617,956
Progress billings and advance payments	(454,119		)	(607,397		)
	$	15,246		$	10,559
Contract cost and recognized income not yet billed	$	26,307		$	20,451
Contract billings in excess of cost and recognized income	(11,061		)	(9,892		)
	$	15,246		$	10,559

Contract cost and recognized income not yet billed includes $0.9 million and $0.8 million at March 31, 2016 and December 31, 2015, respectively, on completed contracts.

The balances billed but not paid by customers pursuant to retainage provisions in certain contracts are generally due upon completion of the contracts and acceptance by the customer. Based on the Company’s experience with similar contracts in recent years, the majority of the retainage balances at each balance sheet date are expected to be collected within the next 12 months. Current retainage balances at March 31, 2016 and December 31, 2015, were approximately $20.7 million and $25.3 million, respectively, and are included in “Accounts receivable, net” in the Condensed Consolidated Balance Sheets. There were no retainage balances with settlement dates beyond the next 12 months at March 31, 2016 and December 31, 2015.