Consolidation Of Variable Interest Entities (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) item	Mar. 31, 2017 USD ($) item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Variable Interest Entity [Line Items]
Net book value	$ 2,106,515,000		$ 2,004,961,000
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Net book value	61,920,000		61,842,000
Cash	22,765,000	$ 20,382,000	$ 20,685,000	$ 30,449,000
Collateralized Financing Obligations [Member]
Variable Interest Entity [Line Items]
Long-term debt	95,100,000
Term Loan [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Long-term debt	$ 2,800,000
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
Net book value	$ 73,800,000
Cash	22,800,000
Gain (loss) recognized on initial consolidation of VIEs	0
Book value of containers sold	$ 7,900,000