Organization and Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 deliverable segment	Dec. 31, 2011 engine	Dec. 31, 2010 engine
Organization and Summary of Significant Accounting Policies
Number of reportable segments	1
Revenue Recognition
Number of engines sold to an investor group		3	4
Proceeds from sale of engines to an investor group		$ 29,000,000	$ 32,900,000
Number of deliverables	2
Gain on sale of engines to an investor group		5,000,000	7,200,000
Lease rent to be received, more than 30 days past due	2,900,000
Maintenance reserve payments to be received, more than 30 days past due	2,700,000
Minimum number of days for which lease rent and maintenance reserve payments are past due	30 days
Revenues | Customer concentration risk | One largest customer
Concentration of credit risks
Percentage of concentration risk	7.40%
Lease rents due	$ 106,000