SCHEDULE I - Parent Company Information - Condensed Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$ 7,247	$ 15,626	$ 1,535
Adjustments to reconcile net income to net cash provided by operating activities:
Write-down of equipment	5,602	6,461	5,874
Stock-based compensation expenses	3,509	3,439	3,144
Amortization of deferred costs	4,319	4,113	3,982
Amortization of interest rate derivative cost	(499)	(404)	(236)
Allowances and provisions	(81)	(684)	503
Gain on sale of leased equipment	(5,753)	(5,675)	(5,499)
Gain on insurance settlement		(351)	(173)
Income from joint ventures	(1,329)	(3,526)	(957)
Non-cash portion of loss on debt extinguishment			7,164
Deferred income taxes	3,996	(4,389)	949
Changes in assets and liabilities:
Receivables	4,454	2,269	(4,985)
Spare parts inventory	5,964
Notes receivable			542
Other assets	(590)	(3,158)	(1,256)
Accounts payable and accrued expenses	(1,881)	(23)	(5,724)
Maintenance reserves	(10,861)	14,022	8,804
Security deposits	1,159	614	678
Unearned lease revenue	793	(1,064)	301
Net cash provided by operating activities	62,731	80,296	67,311
Cash flows from investing activities:
Proceeds from sale of equipment held for operating lease (net of selling expenses)	43,632	38,706	34,607
Capital contribution to joint ventures	(17,623)	(11,219)	(5,636)
Distributions received from joint venture	847
Acquisitions of J.T Power, net of cash acquired		(4,171)
Acquisitions of WOLF, net of cash acquired		2,020
Purchase of equipment held for operating lease	(128,075)	(136,231)	(61,464)
Purchase of property, equipment and furnishings	(13,831)	(453)	(1,219)
Net cash used in investing activities	(108,684)	(131,850)	(31,958)
Cash flows from financing activities:
Proceeds from issuance of notes payable	154,395	130,000	603,693
Debt issuance cost	(5,074)	(1,252)	(11,949)
Preferred stock dividends			(2,493)
Proceeds from shares issued under stock compensation plans	410	680	1,725
Cancellation of restricted stock units in satisfaction of withholding tax	(1,544)	(1,248)	(1,194)
Redemption of preferred stock			(34,750)
Security deposit	4,553	7,588
Repurchase of common stock	(5,352)	(5,918)	(12,736)
Excess tax benefit from stock-based compensation	311
Principal payments on notes payable	(101,054)	(70,874)	(626,923)
Net cash provided by (used in) financing activities	46,645	58,976	(36,414)
Increase (decrease) in cash and cash equivalents	692	7,422	(1,061)
Cash and cash equivalents at beginning of period	12,801	5,379	6,440
Cash and cash equivalents at end of period	13,493	12,801	5,379
Net cash paid for:
Interest	33,132	33,931	21,528
Income Taxes	210	111	105
Supplemental disclosures of non-cash investing activities:
Engines and equipment, transferred from Held for Operating Lease to Held for Sale but not settled	3,071	15,166	22,935
Engines and equipment, transferred to (from) the parent to its subsidiaries	120,880
Equipment Held For Sale Transfer To Spare Parts Inventory	9,649
Parent Company
Cash flows from operating activities:
Net income	7,247	15,626	1,535
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in income of subsidiaries	(7,736)	(19,760)	(6,314)
Depreciation expense	29,555	19,699	18,764
Write-down of equipment	4,681	4,204	2,621
Stock-based compensation expenses	3,509	3,439	3,144
Amortization of deferred costs	2,391	2,286	2,215
Amortization of interest rate derivative cost	(499)	(404)	(236)
Allowances and provisions	34	(94)	34
Gain on sale of leased equipment	(2,147)	(3,472)	(3,605)
Gain on insurance settlement		(351)	(173)
Income from joint ventures	(1,329)	(3,526)	(957)
Non-cash portion of loss on debt extinguishment			94
Deferred income taxes	1,383	(4,072)	(2,408)
Changes in assets and liabilities:
Receivables	(1,502)	1,871	(292)
Spare parts inventory	(5,533)
Notes receivable			5
Other assets	(942)	(2,165)	(1,329)
Accounts payable and accrued expenses	322	(943)	(2,209)
Due to / from subsidiaries	(2,208)	(4,041)	4,946
Maintenance reserves	8,693	3,495	2,898
Security deposits	(1,616)	426	(641)
Unearned lease revenue	919	(575)	335
Net cash provided by operating activities	35,222	11,643	18,427
Cash flows from investing activities:
Increase in investment in subsidiaries	(9,666)	(34,098)	(100,649)
Distributions received from subsidiaries	17,582	69,548	106,183
Proceeds from sale of equipment held for operating lease (net of selling expenses)	21,360	21,644	21,371
Capital contribution to joint ventures	(17,623)	(11,219)	(5,636)
Distributions received from joint venture	847
Acquisitions of J.T Power, net of cash acquired		(4,171)
Acquisitions of WOLF, net of cash acquired		(1,000)
Purchase of equipment held for operating lease	(104,904)	(132,140)	(40,465)
Purchase of property, equipment and furnishings	(13,767)	(450)	(1,219)
Net cash used in investing activities	(106,171)	(91,886)	(20,415)
Cash flows from financing activities:
Proceeds from issuance of notes payable	154,395	130,000	236,392
Debt issuance cost	(5,074)	(637)	(516)
Preferred stock dividends			(2,493)
Proceeds from shares issued under stock compensation plans	410	680	1,725
Cancellation of restricted stock units in satisfaction of withholding tax	(1,544)	(1,248)	(1,194)
Redemption of preferred stock			(34,750)
Security deposit	4,553	7,588
Repurchase of common stock	(5,352)	(5,918)	(12,736)
Excess tax benefit from stock-based compensation	311
Principal payments on notes payable	(75,859)	(52,844)	(186,727)
Net cash provided by (used in) financing activities	71,840	77,621	(299)
Increase (decrease) in cash and cash equivalents	891	(2,622)	(2,287)
Cash and cash equivalents at beginning of period	1,520	4,142	6,429
Cash and cash equivalents at end of period	2,411	1,520	4,142
Net cash paid for:
Interest	11,110	11,903	8,105
Income Taxes	76	111	101
Supplemental disclosures of non-cash investing activities:
Engines and equipment, transferred from Held for Operating Lease to Held for Sale but not settled	3,071	422	14,156
Engines and equipment, transferred to (from) the parent to its subsidiaries		$ 116,020	$ (56,562)