Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Depreciation expense									$ 110,952,000	$ 104,877,000	$ 113,590,000
Net income									$ 72,060,000	$ 6,034,000	$ 26,735,000
Earnings Per Share, Diluted	$ 1.81	$ 0.90	$ 0.65	$ 0.27	$ 0.03	$ (0.28)	$ 0.19	$ 0.36	$ 3.68	$ 0.31	$ 1.27
Impairment charges									$ 0	$ 0	$ 24,500,000
Goodwill	$ 15,794,000				$ 15,794,000				15,794,000	15,794,000
Impairment of goodwill									$ 0
Percentage of general reserve on receivables one to thirty days overdue									1.00%
Percentage of reserve on receivables one year overdue									100.00%
Accounts receivable	70,598,000				63,745,000				$ 70,598,000	63,745,000
Maximum period for general reserve with specific maximum percentage									1 year
Unamortized debt issuance cost	11,700,000				11,200,000				$ 11,700,000	11,200,000
Benefit on Provision for Income Taxes									$ 14,861,000	(3,844,000)	(4,252,000)
Furniture And Fixtures [Member]
Significant Accounting Policies [Line Items]
Estimated useful life									5 years
Residual value	0								$ 0
20-ft. Standard Dry Van Container [Member]
Significant Accounting Policies [Line Items]
Estimated useful life									13 years
Residual value	1,050								$ 1,050
40-ft. Standard Dry Van Container [Member]
Significant Accounting Policies [Line Items]
Estimated useful life									13 years
Residual value	1,300								$ 1,300
40-ft. High Cube Dry Van Container [Member]
Significant Accounting Policies [Line Items]
Estimated useful life									13 years
Residual value	1,400								$ 1,400
20-ft. Refrigerated Container [Member]
Significant Accounting Policies [Line Items]
Estimated useful life									12 years
Residual value	2,750								$ 2,750
40-ft. High Cube Refrigerated Container [Member]
Significant Accounting Policies [Line Items]
Estimated useful life									12 years
Residual value	3,500								$ 3,500
Railcars [Member]
Significant Accounting Policies [Line Items]
Estimated useful life									43 years
Residual value	8,700								$ 8,700
Accounting Standards Update 2016-09 [Member]
Significant Accounting Policies [Line Items]
Deferred tax asset	1,000,000								1,000,000
Benefit on Provision for Income Taxes									1,800,000
Managed Fleet [Member]
Significant Accounting Policies [Line Items]
Accounts receivable	2,300,000				5,100,000				2,300,000	5,100,000
Reclassification [Member] | 40-ft. High Cube Dry Van Container [Member]
Significant Accounting Policies [Line Items]
Residual value	1,400				$ 1,650				1,400	1,650
Depreciation expense									4,400,000	5,400,000
Net income									$ 4,300,000	$ 5,200,000
Earnings Per Share, Diluted									$ 0.22	$ 0.27
Minimum [Member]
Significant Accounting Policies [Line Items]
Period for general reserve with specific minimum percentage									1 day
Minimum [Member] | Other Specialized Equipment [Member]
Significant Accounting Policies [Line Items]
Estimated useful life									12 years 6 months
Residual value	1,000								$ 1,000
Maximum [Member]
Significant Accounting Policies [Line Items]
Period for general reserve with specific minimum percentage									30 days
Maximum [Member] | Other Specialized Equipment [Member]
Significant Accounting Policies [Line Items]
Estimated useful life									15 years
Residual value	$ 3,500								$ 3,500
Retained Earnings [Member]
Significant Accounting Policies [Line Items]
Net income									$ 72,060,000	$ 5,997,000	$ 26,601,000