Business Segment And Geographic Area Information (Narrative) (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Number of reportable segments	1
Percentage of revenue from government contracts	99.20%	98.70%	98.30%
Threshold percentage for customer disclosure	10.00%
Sales Revenue, Segment [Member]
Threshold percentage for major contracts	10.00%	10.00%	10.00%
Operating Income [Member]
Threshold percentage for major contracts	10.00%	10.00%	10.00%
Receivables [Member]
Threshold percentage for major contracts	10.00%	10.00%