Long Term Debt (Details 2) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Sep. 17, 2012 engine	Dec. 31, 2014
Long Term Debt
Net proceeds received from notes issued and sold	$ 31,000,000	$ 5,000,000
Total notes payable	842,177,000			840,956,000
WEST II Series 2012-A term notes payable at a fixed rate of interest maturing in September 2037. Secured by engines | WEST II
Long Term Debt
Face amount			390,000,000
Net proceeds received from notes issued and sold			384,900,000
Debt Instrument Expected Payoff Period	10 years
Total notes payable	346,900,000			351,900,000
Number of engines pledged as collateral	68		22
Fixed amortization of notes payable	0
Fixed rate (as a percent)	5.50%
Number of business days to pay interest	5 days
Period of time over which maintenance obligations are projected	6 months
WEST II Series 2012-A term notes payable at a fixed rate of interest maturing in September 2037. Secured by engines | WEST II | Minimum
Long Term Debt
Minimum amount of cash from maintenance reserve payments required to be held in restricted cash account	9,000,000
Prior WEST notes
Long Term Debt
Total notes payable			$ 435,900,000