Income Taxes (Summary of Unrecognized Tax Benefits and Temporary Differences) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Unrecognized tax benefits
Balance at the beginning of the period		$ 191,000	$ 206,000	$ 274,000	$ 464,000
Increases related to current year tax positions			4,000	4,000	5,000
Decreases due to tax positions expired			(19,000)	(72,000)	(195,000)
Balance at the end of the period	$ 191,000		191,000	206,000	$ 274,000
Uncertain tax positions, reserved for tax exposure in Europe	0		0	0
Deferred tax assets:
Unearned lease revenue	1,754,000		1,754,000	1,839,000
State taxes	1,653,000		1,653,000	1,035,000
Reserves and allowances	2,531,000		2,531,000	1,659,000
Other accruals	643,000		643,000	2,501,000
Alternative minimum tax credit				335,000
Foreign tax credit	42,000		42,000	42,000
Net operating loss carry forward	29,874,000		29,874,000	35,693,000
Charitable contributions	22,000		22,000	52,000
Total deferred tax assets	36,519,000		36,519,000	43,156,000
Less: valuation allowance	(806,000)		(806,000)	(1,280,000)
Net deferred tax assets	35,713,000		35,713,000	41,876,000
Deferred tax liabilities:
Depreciation and impairment on aircraft engines and equipment	(114,347,000)		(114,347,000)	(147,827,000)
Other deferred tax assets (liabilities)	437,000		437,000	422,000
Net deferred tax liabilities	(113,910,000)		(113,910,000)	(147,405,000)
Other comprehensive income, deferred tax asset	(83,000)		(83,000)	551,000
Net deferred tax liabilities	(78,280,000)		$ (78,280,000)	$ (104,978,000)
Valuation allowance of net operating loss						$ 1,300,000
Statutory federal income tax expense (as a percent)			35.00%
Additional income tax benefit	39,600,000
Provisional amount	43,600,000
Reduction in tax expenses	4,000,000
Scenario, Forecast [Member]
Deferred tax liabilities:
Statutory federal income tax expense (as a percent)		21.00%
Federal
Deferred tax assets:
Alternative minimum tax credit	400,000		$ 400,000
Deferred tax liabilities:
Operating loss carryforwards	138,000,000		138,000,000
Valuation allowance of net operating loss	0		$ 0
Federal | Minimum
Deferred tax liabilities:
Alternative minimum tax credit period			2 years
Federal | Maximum
Deferred tax liabilities:
Alternative minimum tax credit period			4 years
State
Deferred tax liabilities:
Operating loss carryforwards	$ 1,000,000		$ 1,000,000