Consolidation Of Variable Interest Entities (Details)	3 Months Ended
	Mar. 31, 2021 USD ($) item	Mar. 31, 2020 USD ($) item	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Variable Interest Entity [Line Items]
Net book value	$ 1,808,001,000		$ 1,781,321,000
Collateralized Financing Obligations [Member]
Variable Interest Entity [Line Items]
Long-term debt	61,600,000
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Net book value	73,212,000		77,907,000
Cash	23,942,000	$ 21,016,000	$ 26,856,000	$ 26,594,000
Variable Interest Entity, Primary Beneficiary [Member] | Term Loan [Member]
Variable Interest Entity [Line Items]
Long-term debt	$ 29,900,000
Variable Interest Entity, Primary Beneficiary [Member] | Containers [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	$ 75,400,000
Cash	23,900,000
Gain (loss) recognized on initial consolidation of VIEs	$ 0
Number of containers sold | item	0	0