Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Significant Accounting Policies
Inventory reserves	$ 25,862,000		$ 25,862,000		$ 24,948,000
Unbilled receivables	$ 36,800,000		$ 36,800,000		$ 26,500,000
Percentage of total revenue	20.00%	22.00%	23.00%	19.00%
Percentage of product revenue	24.00%	26.00%	27.00%	22.00%
Number of projects	12	11	12	14

The amount of the valuation account as of the balance sheet date which reduces the carrying amount of inventory to net realizable value; takes into consideration such factors as market value, excessive quantities based on expected sales, technological obsolescence, and shrinkage. May also provide for estimated product returns or price concessions pertaining to product cost.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Chapter 4
-Paragraph 8, 9, 14

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 09
-Article 12

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 6
-Subparagraph a
-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Chapter 3
-Section A
-Paragraph 9

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Chapter 4
-Paragraph 14

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant