4. RECEIVABLES

Receivables include current notes, amounts billed to customers, claims, other receivables, and unbilled revenue on long-term contracts, consisting of amounts recognized as sales but not billed. Substantially all amounts of unbilled receivables are expected to be billed and collected in the subsequent year. An immaterial amount of unbilled receivables are subject to retainage provisions. The amount of claims and unapproved change orders within our receivables balances are immaterial.

Credit risk is diversified due to the large number of entities comprising the Corporation’s customer base and their geographic dispersion. The Corporation is either a prime contractor or subcontractor to various agencies of the U.S. Government. Revenues derived directly and indirectly from government sources (primarily the U.S. Government) were 30% and 37% of consolidated revenues in 2013 and 2012, respectively. Total receivables due primarily from the U.S Government were $205.1 million and $201.6 million at December 31, 2013 and 2012, respectively. Government (primarily the U.S. Government) unbilled receivables, net of progress payments, were $82.5 million and $87.6 million at December 31, 2013 and 2012, respectively.

The composition of receivables is as follows as of December 31:



(In thousands)	2013			2012
Billed receivables:
Trade and other receivables	$	444,841		$	402,891
Less: Allowance for doubtful accounts	(6,857		)	(7,013		)
Net billed receivables	437,984			395,878
Unbilled receivables:
Recoverable costs and estimated earnings not billed	184,120			207,679
Less: Progress payments applied	(18,512		)	(25,244		)
Net unbilled receivables	165,608			182,435
Receivables, net	$	603,592		$	578,313

The net receivable balance at December 31, 2013, included $32.0 million related to the Corporation’s 2013 acquisitions.