Maintenance and Accrued Costs, 2 (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Accrued maintenance cost [Roll Forward]
Balance, beginning of period			$ 1,013,400	$ 2,446,800
Additions [Abstract]
Charged to expense			2,378,500	7,909,000
Reversals of previously accrued maintenance costs			(11,400)	(401,300)
Total maintenance expense	1,612,600	2,939,700	2,367,100	7,507,700
Capital equipment			64,800	242,600
Accrued claims related to refundable maintenance reserves			578,100	81,200
Prepaid maintenance			32,900	201,100
Total additions			3,042,900	8,032,600
Deductions [Abstract]
Payments			1,960,500	6,915,500
Other			479,800	607,000
Total deductions			2,440,300	7,522,500
Net increase in accrued maintenance costs			602,600	510,100
Balance, end of period	$ 1,616,000	$ 2,956,900	$ 1,616,000	$ 2,956,900