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v2.4.1.9

Pension and Other Post-Retirement Benefits (Details 9) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014
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Qualified Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
2015 | $ 28.2 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths / gmt_DefinedBenefitPlansAxis = gmt_QualifiedPlansMember
2016 | 28.3 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo / gmt_DefinedBenefitPlansAxis = gmt_QualifiedPlansMember
2017 | 28.7 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree / gmt_DefinedBenefitPlansAxis = gmt_QualifiedPlansMember
2018 | 29.2 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour / gmt_DefinedBenefitPlansAxis = gmt_QualifiedPlansMember
2019 | 29.6 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive / gmt_DefinedBenefitPlansAxis = gmt_QualifiedPlansMember
Years 2020-2024 | 152.2 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter / gmt_DefinedBenefitPlansAxis = gmt_QualifiedPlansMember
Total | 296.2 gmt_DefinedBenefitPlanEstimatedFutureBenefitPayments / gmt_DefinedBenefitPlansAxis = gmt_QualifiedPlansMember
Nonqualified Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
2015 | 2.0 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths / gmt_DefinedBenefitPlansAxis = gmt_NonqualifiedPlansMember
2016 | 2.2 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo / gmt_DefinedBenefitPlansAxis = gmt_NonqualifiedPlansMember
2017 | 2.3 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree / gmt_DefinedBenefitPlansAxis = gmt_NonqualifiedPlansMember
2018 | 2.3 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour / gmt_DefinedBenefitPlansAxis = gmt_NonqualifiedPlansMember
2019 | 2.8 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive / gmt_DefinedBenefitPlansAxis = gmt_NonqualifiedPlansMember
Years 2020-2024 | 15.3 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter / gmt_DefinedBenefitPlansAxis = gmt_NonqualifiedPlansMember
Total | 26.9 gmt_DefinedBenefitPlanEstimatedFutureBenefitPayments / gmt_DefinedBenefitPlansAxis = gmt_NonqualifiedPlansMember
Other Benefits [Member] |
Defined Benefit Plan Disclosure [Line Items] |
2015 | 3.5 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths / gmt_DefinedBenefitPlansAxis = gmt_OtherBenefitsMember
2016 | 3.4 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo / gmt_DefinedBenefitPlansAxis = gmt_OtherBenefitsMember
2017 | 3.3 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree / gmt_DefinedBenefitPlansAxis = gmt_OtherBenefitsMember
2018 | 3.2 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour / gmt_DefinedBenefitPlansAxis = gmt_OtherBenefitsMember
2019 | 3.1 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive / gmt_DefinedBenefitPlansAxis = gmt_OtherBenefitsMember
Years 2020-2024 | 14.0 us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter / gmt_DefinedBenefitPlansAxis = gmt_OtherBenefitsMember
Total | $ 30.5 gmt_DefinedBenefitPlanEstimatedFutureBenefitPayments / gmt_DefinedBenefitPlansAxis = gmt_OtherBenefitsMember

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- Definition Amount of benefits from a defined benefit plan expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition Amount of benefits from a defined benefit plan expected to be paid in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition Amount of benefits from a defined benefit plan expected to be paid in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition Amount of benefits from a defined benefit plan expected to be paid in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition Amount of benefits from a defined benefit plan expected to be paid in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition Amount of benefits from a defined benefit plan expected to be paid in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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