Notes Payable (Details) (USD $)	12 Months Ended			0 Months Ended		12 Months Ended			12 Months Ended	0 Months Ended	12 Months Ended		0 Months Ended	12 Months Ended		0 Months Ended				0 Months Ended		12 Months Ended			0 Months Ended	12 Months Ended			0 Months Ended				12 Months Ended		3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Sep. 18, 2013 WOLF	Sep. 17, 2012 WEST II Series 2012-A term notes payable at a fixed rate of interest maturing in September 2037. Secured by engines WEST II	Dec. 31, 2013 WEST II Series 2012-A term notes payable at a fixed rate of interest maturing in September 2037. Secured by engines WEST II item	Dec. 31, 2012 WEST II Series 2012-A term notes payable at a fixed rate of interest maturing in September 2037. Secured by engines WEST II	Dec. 31, 2013 WEST II Series 2012-A term notes payable at a fixed rate of interest maturing in September 2037. Secured by engines WEST II Minimum	Dec. 31, 2013 Note payable at a fixed interest rate of 4.00%, maturing in May 2017, secured by engines	Jan. 11, 2010 Note payable at a fixed interest rate of 4.50%, maturing in January 2014. Secured by engines.	Dec. 31, 2013 Note payable at a fixed interest rate of 4.50%, maturing in January 2014. Secured by engines. engine	Dec. 31, 2012 Note payable at a fixed interest rate of 4.50%, maturing in January 2014. Secured by engines.	Sep. 28, 2012 Note payable at a fixed interest rate of 5.50%, maturing in September 2017. Secured by one engine.	Dec. 31, 2013 Note payable at a fixed interest rate of 5.50%, maturing in September 2017. Secured by one engine. engine	Dec. 31, 2012 Note payable at a fixed interest rate of 5.50%, maturing in September 2017. Secured by one engine.	Sep. 30, 2011 Note payable at a fixed interest rate of 3.94%, maturing in September 2014. Secured by an aircraft	Dec. 31, 2013 Note payable at a fixed interest rate of 3.94%, maturing in September 2014. Secured by an aircraft	Dec. 31, 2012 Note payable at a fixed interest rate of 3.94%, maturing in September 2014. Secured by an aircraft	Sep. 17, 2012 Prior WEST notes	Jan. 10, 2014 Note payable at a fixed interest rate of 2.25%, maturing in January 2018, secured by three engines Subsequent event engine	Jan. 10, 2014 Note payable at a fixed interest rate of 2.25%, maturing in January 2018, secured by three engines Subsequent event LIBOR	Dec. 31, 2013 Notes payable	Dec. 31, 2013 Notes payable Minimum	Dec. 31, 2013 Notes payable Maximum	Nov. 18, 2011 Revolving credit facility	Dec. 31, 2013 Revolving credit facility	Jun. 18, 2013 Revolving credit facility	Dec. 31, 2012 Revolving credit facility	Sep. 17, 2012 Revolving credit facility WEST engine	Dec. 31, 2013 Revolving credit facility Credit agreement	Dec. 31, 2013 Revolving credit facility Credit agreement Minimum	Dec. 31, 2013 Revolving credit facility Credit agreement Maximum	Dec. 31, 2013 Credit facility at a floating rate of interest of LIBOR plus 3.00%, secured by engines	Dec. 31, 2012 Credit facility at a floating rate of interest of LIBOR plus 3.00%, secured by engines	Dec. 31, 2013 Term notes WOLF	Sep. 30, 2013 Term notes WOLF	Sep. 18, 2013 Term notes WOLF item
Long Term Debt
Variable rate of debt									LIBOR												one-month LIBOR												LIBOR		one-month LIBOR
Basis spread on variable rate (as a percent)									4.00%												2.25%												3.00%		4.00%
Maximum borrowing capacity under credit facility																										$ 450,000,000	$ 450,000,000	$ 430,000,000					$ 450,000,000	$ 430,000,000
Fixed rate (as a percent)						5.50%					4.50%			5.50%			3.94%
Total notes payable before discount	787,614,000	696,988,000				370,614,000	386,724,000		30,000,000		15,827,000	17,338,000		8,173,000	8,593,000		1,000,000	2,333,000	435,900,000														362,000,000	282,000,000		30,000,000
One-month LIBOR rate (as a percent)	0.17%	0.21%
Principal outstanding repayable
2014	42,024,000
2015	32,934,000
2016 (includes $362.0 million outstanding on revolving credit facility)	388,215,000
2017	37,373,000
2018	23,468,000
Thereafter	263,600,000
Notes payable	787,614,000	696,988,000				370,614,000	386,724,000		30,000,000		15,827,000	17,338,000		8,173,000	8,593,000		1,000,000	2,333,000	435,900,000														362,000,000	282,000,000		30,000,000
Line of credit facility outstanding amount	362,000,000
Interest coverage ratio																															2.50
Leverage ratio																																4.75
Minimum consolidated tangible net worth																														196,100,000
Notes payable	787,614,000	696,988,000																				787,600,000
Maturity term						10 years				4 years			5 years			3 years							1 month	9 years
Interest rate, minimum (as a percent)																						3.20%
Interest rate, maximum (as a percent)																						5.50%
Remaining borrowing capacity available																										88,000,000		148,000,000
Debt issuance costs																									3,300,000
Maximum borrowing capacity under credit facility before amendment																											430,000,000
Debt to equity ratio																										3.87
Face amount					390,000,000					22,000,000			8,700,000			4,000,000																					36,000,000
Net proceeds received from notes issued and sold	130,000,000	603,693,000	132,409,000		384,900,000
Number of engines pledged as collateral											3			1						3									22
Number of engines in portfolio offered as collateral						71
Fixed amortization of notes payable						0
Number of business days to pay interest						5 days
Period of time over which maintenance obligations are projected						6 months
Minimum amount of cash from maintenance reserve payments required to be held in restricted cash account								$ 9,000,000
Acquisition of remaining outstanding shares of previously held equity method investment (as a percent)				50.00%
Controlling interest assumed (as a percent)				100.00%
Number of term notes held																																					2
Extended maturity term																				4 years