Consolidation Of Variable Interest Entities (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) item	Sep. 30, 2017 USD ($) item	Sep. 30, 2018 USD ($) item	Sep. 30, 2017 USD ($) item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Variable Interest Entity [Line Items]
Net book value	$ 2,299,955,000		$ 2,299,955,000		$ 2,004,961,000
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Net book value	73,110,000		73,110,000		61,842,000
Cash	23,779,000	$ 22,445,000	23,779,000	$ 22,445,000	$ 20,685,000	$ 30,449,000
Collateralized Financing Obligations [Member]
Variable Interest Entity [Line Items]
Long-term debt	103,100,000		103,100,000
Term Loan [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Long-term debt	$ 1,900,000		$ 1,900,000
Containers [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Number of types of container fund arrangements | item			2
Number of container portfolios sold | item	0	0	0	0
Net book value	$ 82,500,000		$ 82,500,000
Cash	23,800,000		23,800,000
Gain (loss) recognized on initial consolidation of VIEs			0
Book value of containers sold	$ 14,600,000	$ 6,000,000	$ 29,800,000	$ 13,200,000