XML 198 R60.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Supplemental Cash Flow and Noncash Investing Transactions (Details Textual) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 USD ($) Car | Dec. 31, 2013 USD ($) Car | Dec. 31, 2012 USD ($) | Dec. 31, 2013 Singco/Somagas [Member] USD ($) | Dec. 31, 2014 Aae Cargo Ag [Member] USD ($) | Dec. 31, 2013 Aae Cargo Ag [Member] USD ($) | Dec. 31, 2012 Aae Cargo Ag [Member] USD ($) | Dec. 31, 2014 Aae Cargo Ag [Member] USD ($) | Dec. 31, 2014 Aae Cargo Ag [Member] EUR (€) | Dec. 31, 2013 Aae Cargo Ag [Member] USD ($) | Dec. 31, 2013 Aae Cargo Ag [Member] EUR (€)
Noncash or Part Noncash Divestitures [Line Items] |  |  |  |  |  |  |  |  |  |  |
Portfolio proceeds | $ 264.0 gmt_PortfolioProceeds | $ 385.3 gmt_PortfolioProceeds | $ 288.9 gmt_PortfolioProceeds |  | $ 0 gmt_PortfolioProceeds / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = gmt_AaeCargoAgMember | $ 91.1 gmt_PortfolioProceeds / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = gmt_AaeCargoAgMember | $ 0 gmt_PortfolioProceeds / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = gmt_AaeCargoAgMember | $ 77.0 gmt_PortfolioProceeds / gmt_VariableInterestEntitiesByClassificationOfAssetsAxis = gmt_AaeCargoAgMember | € 68.2 gmt_PortfolioProceeds / gmt_VariableInterestEntitiesByClassificationOfAssetsAxis = gmt_AaeCargoAgMember | $ 91.1 gmt_PortfolioProceeds / gmt_VariableInterestEntitiesByClassificationOfAssetsAxis = gmt_AaeCargoAgMember | € 67.5 gmt_PortfolioProceeds / gmt_VariableInterestEntitiesByClassificationOfAssetsAxis = gmt_AaeCargoAgMember
Supplemental Cash Flow and Noncash Investing and Financing Transactions (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |
Aggregate fair value of liquidating distributions | $ 1.1 us-gaap_FairValueOfAssetsAcquired | $ 22.9 us-gaap_FairValueOfAssetsAcquired | $ 0 us-gaap_FairValueOfAssetsAcquired | $ 151.8 us-gaap_FairValueOfAssetsAcquired / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = gmt_SingcoSomagasMember |  |  |  |  |  |  |
Number of railcars received | 62 gmt_Numberofrailcarsreceived | 640 gmt_Numberofrailcarsreceived |  |  |  |  |  |  |  |  |

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 Portfolio proceeds. + References No definition available. + Details
Name: | gmt_PortfolioProceeds
Namespace Prefix: | gmt_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | gmt_SupplementalCashFlowAndNoncashInvestingAndFinancingTransactionsTextualAbstract
Namespace Prefix: | gmt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The fair value of assets acquired in noncash investing or financing activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586 + Details
Name: | us-gaap_FairValueOfAssetsAcquired
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_NoncashOrPartNoncashDivestituresLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration