Organization and Summary of Significant Accounting Policies (Details 3) (USD $) Share data in Thousands, unless otherwise specified	1 Months Ended	3 Months Ended												12 Months Ended
	Nov. 30, 2010	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2012 item	Dec. 31, 2011	Dec. 31, 2010
Restricted Cash
Minimum amount of cash from maintenance reserve payments required to be held in restricted cash account		$ 9,000,000												$ 9,000,000
Projected maintenance obligation period														6 months
Shares:
Weighted-average number of common shares outstanding		8,277	8,667	8,585	8,404	8,425	8,397	8,322	8,552	8,654	8,683	8,729	8,660	8,490	8,423	8,681
Potentially dilutive common shares														301	453	570
Total shares		8,525	8,889	8,848	8,756	8,758	8,811	8,796	9,048	9,199	9,080	9,255	9,303	8,791	8,876	9,251
Potential common stock excluded as anti-dilutive in period (in shares)																4
Investments
Number of investments in joint ventures														2
Ownership interest (as a percent)		50.00%												50.00%
Proceeds from sale of interest in joint venture	3,500,000															3,500,000
Gain on sale of interest in joint venture	2,000,000															2,020,000
Initial Direct Costs associated with Leases
Amortization of initial direct costs associated with leases														$ 1,600,000	$ 1,400,000	$ 1,600,000
Minimum
Property, Equipment and Furnishings
Useful life of property, equipment and furnishings														3 years
Maximum
Property, Equipment and Furnishings
Useful life of property, equipment and furnishings														5 years