XML 103 R62.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Leases (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 USD ($) tankContainer railcar | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) tankContainer
Operating Leased Assets [Line Items] |  |  |
Number of railcars received | tankContainer | 728 |  | 21
Lessee, Lease, Number of Railcars Leased | railcar | 4,432,000,000 |  |
Direct Financing Lease, Lease Income | $ 13.5 | $ 12.6 | $ 9.8
Operating Lease, Lease Income, Lease Payments | 1,263.5 | 1,145.1 | 1,058.3
Operating Lease, Variable Lease Income | 104.1 | 93.7 | 86.5
Operating Lease, Lease Income | 1,367.6 | 1,238.8 | 1,144.8
Lease Income | 1,381.1 | 1,251.4 | $ 1,154.6
Total contractual lease payments receivable | 160.0 | 171.8 |
Estimated unguaranteed residual value of leased assets | 17.2 | 17.2 |
Unearned income | (58.9) | (52.6) |
Finance leases | $ 118.3 | $ 136.4 |

X
- Definition Lessee, Lease, Number of Railcars Leased + References No definition available. + Details
Name: | gmt_LesseeLeaseNumberofRailcarsLeased
Namespace Prefix: | gmt_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of railcars received + References No definition available. + Details
Name: | gmt_Numberofrailcarsreceived
Namespace Prefix: | gmt_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of deferred selling profit from direct financing lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-6 + Details
Name: | us-gaap_DirectFinancingLeaseDeferredSellingProfit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of lease income from variable lease payments, interest income on direct financing lease and after offset of loss recognized at commencement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-5 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 270 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482964/270-10-50-6A Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479016/842-30-45-3 + Details
Name: | us-gaap_DirectFinancingLeaseLeaseIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Present value of lease payments not yet received by lessor and amount expected to be derived from underlying asset, following end of lease term, guaranteed by lessee or other third party unrelated to lessor, from direct financing lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-6 + Details
Name: | us-gaap_DirectFinancingLeaseLeaseReceivable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, before allowance for credit loss, of net investment in direct financing lease. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 7A -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-7A Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-14 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-6 + Details
Name: | us-gaap_DirectFinancingLeaseNetInvestmentInLease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Present value expected to be derived from underlying asset, following end of lease term, not guaranteed by lessee or other third party unrelated to lessor. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-6 + Details
Name: | us-gaap_DirectFinancingLeaseUnguaranteedResidualAsset
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of lease income from operating, direct financing, and sales-type leases. Includes, but is not limited to, variable lease payments, interest income, profit (loss) recognized at commencement, and lease payments paid and payable to lessor. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-5 + Details
Name: | us-gaap_LeaseIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-5 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 270 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482964/270-10-50-6A Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479016/842-30-45-3 + Details
Name: | us-gaap_OperatingLeaseLeaseIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of operating lease income from lease payments paid and payable to lessor. Excludes variable lease payments not included in measurement of lease receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 270 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482964/270-10-50-6A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-5 + Details
Name: | us-gaap_OperatingLeaseLeaseIncomeLeasePayments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of operating lease income from variable lease payments paid and payable to lessor, excluding amount included in measurement of lease receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-5 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 270 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482964/270-10-50-6A + Details
Name: | us-gaap_OperatingLeaseVariableLeaseIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_OperatingLeasedAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration