Supplemental Cash Flow and Noncash Investing Transactions (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) railcar	Dec. 31, 2019 USD ($) railcar	Dec. 31, 2018 USD ($)
Noncash or Part Noncash Divestitures [Line Items]
Number of railcars received \| railcar	732	157
Supplemental Cash Flow Information
Interest Paid, Excluding Capitalized Interest, Operating Activities	$ 189.8	$ 185.1	$ 164.0
Income taxes paid (refunded), net	21.4	11.6	18.1
Portfolio proceeds	$ 131.1	$ 250.3	$ 234.4

Amount of cash paid for interest, excluding capitalized interest, classified as operating activity. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121583591&loc=d3e4297-108586

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3367-108585

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3536-108585

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