Business Segments, Concentration of Credit Risk and Significant Customers (Details 2)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Total revenues | Customer concentration risk | Customer A
Significant Customers
Percentage of concentration risk	28.00%	23.00%	18.00%
Total revenues | Customer concentration risk | Customer B
Significant Customers
Percentage of concentration risk	26.00%	12.00%
Total revenues | Customer concentration risk | Customer C
Significant Customers
Percentage of concentration risk	12.00%	17.00%	23.00%
Total revenues | Customer concentration risk | Customer D
Significant Customers
Percentage of concentration risk			15.00%
Net accounts receivable | Credit concentration | Three customers
Significant Customers
Percentage of concentration risk	100.00%
Number of customers	3
Net accounts receivable | Credit concentration | Four customers
Significant Customers
Percentage of concentration risk		96.00%
Number of customers		4