Long-term Debt (Details Textual) (USD $)	12 Months Ended					1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended	0 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Lease Fleet Financing [Member]	Dec. 31, 2012 Lease Fleet Financing [Member]	Dec. 31, 2012 Term Loan [Member] Loan	Dec. 31, 2013 Term Loan [Member]	Jun. 30, 2013 Term Loan [Member] Loan	Dec. 31, 2013 Term Loan [Member]	Mar. 01, 2013 Senior Unsecured Notes [Member]	Sep. 04, 2012 Senior Unsecured Notes [Member]	Feb. 28, 2007 Senior Unsecured Notes [Member]	Dec. 31, 2013 London Interbank Offered Rate (LIBOR) [Member] Term Loan [Member]
Debt Instrument [Line Items]
Net of fees and expenses						$ 98,400,000			$ 99,400,000
Outstanding principal balance on term loan						100,000,000	194,800,000		194,800,000	175,000,000
Number of additional draws on term loan						2
Number of additional draws incurred								2
Line of credit, additional borrowings								99,800,000
Percentage of interest on term loan													2.50%
Percentage of interest on term loan rate							2.70%		2.70%
Percentage of increase in term loan interest									2.00%
Interest reserve amount for term loan							3,900,000		3,900,000
Percentage of principal amount payment									3.33%
Minimum Loan to Value Percentage of Net Aggregate Equipment Value									75.00%
Leasing debt service coverage ratio									1.05
Term loan cure period									75 days
Restrictive debt service coverage ratio							1.2
Net book value of property	372,551,000	220,282,000		216,700,000	112,000,000
Initial value of debt												275,000,000.0
Notes redeemed											100,000,000
Extinguishment Of Debt As Percentage Of Principal Amount											101.875%
Fixed interest rate of the notes which are due in 2014												7.50%
Loss on debt extinguishment	392,000	2,267,000	0							400,000	(2,300,000)
Premium paid on debt redemption	0	1,875,000	0								1,900,000
Write off of Deferred Debt Issuance Cost											$ 400,000