SUMMARY OF QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) (Details 8) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Accounts receivable:
Trade and other receivables	$ 17,352				$ 17,543
Long-term contracts:
Allowance for doubtful accounts	(658)				(463)
Less estimated amounts not currently due	19,021	19,698	20,678	21,308	21,918	22,774	23,514	24,064
Current accounts receivable	379,002	385,937	410,762	355,977	348,971	318,649	287,513	249,063
Inventories
Work in process and inventoried costs under long-term contracts	80,918				68,525
Customer advances	(21,865)				(27,288)
Materials and purchased parts	693				858
Net inventories	59,746	42,377	39,787	42,517	42,095	46,665	53,214	45,876
Interim Financial Information
Accounts receivable:
Trade and other receivables		16,995	21,025	19,701		16,581	13,623	21,684
Long-term contracts:
Billed		81,867	108,774	84,961		99,252	87,000	86,847
Unbilled		307,405	302,292	273,044		226,261	211,074	165,136
Allowance for doubtful accounts		(632)	(651)	(421)		(671)	(670)	(540)
Total accounts receivable		405,635	431,440	377,285		341,423	311,027	273,127
Less estimated amounts not currently due		(19,698)	(20,678)	(21,308)		(22,774)	(23,514)	(24,064)
Current accounts receivable		385,937	410,762	355,977		318,649	287,513	249,063
Inventories
Work in process and inventoried costs under long-term contracts		74,043	60,680	74,833		70,139	85,541	73,455
Customer advances		(32,164)	(21,601)	(33,086)		(24,211)	(33,378)	(28,708)
Materials and purchased parts		498	708	770		737	1,051	1,129
Net inventories		$ 42,377	$ 39,787	$ 42,517		$ 46,665	$ 53,214	$ 45,876