Investments (Details) (USD $)	6 Months Ended			1 Months Ended	6 Months Ended		12 Months Ended			6 Months Ended	1 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jun. 30, 2011 WMES item	Jun. 30, 2012 WMES item	Dec. 31, 2011 WMES	Jun. 30, 2012 WMES item	May 25, 2011 WMES	Jun. 30, 2012 WMES JA Mitsui Leasing, Ltd	Jun. 30, 2012 WMES BOT Lease Co., Ltd.	Dec. 31, 2005 WOLF item	Jun. 30, 2012 WOLF	Dec. 31, 2011 WOLF	Jun. 30, 2011 WOLF	Jun. 30, 2012 WOLF Minimum	Jun. 30, 2012 WOLF Maximum
Investments
Ownership interest (as a percent)					50.00%		50.00%					50.00%
Initial capital contribution								$ 8,000,000
Additional capital contributions	2,868,000	7,995,000			2,868,000	1,000,000
Number of V2500 engines transfer to joint venture				7
Number of engines purchased							5
Number of engines in lease portfolio					12
Capital contributions to date					11,900,000		11,900,000
Proportionate gain on sale of engines to joint venture interest which is off-set against investments					3,600,000
Net investment after deducting partial offset					8,400,000		8,400,000
Gain on sale of engines					7,200,000
Credit facility established by equity method investee					15,000,000		15,000,000		180,000,000
Reference rate, description	one-month LIBOR	one-month LIBOR								one-month LIBOR		one-month LIBOR
Margin (as a percent)										2.90%					1.00%	2.50%
Maturity term										7 years
Investment in joint venture	18,427,000		15,239,000		8,364,000	5,376,000	8,364,000					10,063,000	9,863,000	9,600,000
Number of Airbus A340-313 aircraft purchased											2
Purchase price of aircraft											96,000,000
Number of term notes held											4
Number of financial institutions associated with funding of term notes											1
Loan for purchase of aircraft											$ 76,800,000