Asset Impairment Asset Impairment (Notes)	9 Months Ended
Sep. 30, 2015
Asset Impairment [Abstract]
Asset Impairment Charges [Text Block]	NOTE 5. Asset Impairments GATX previously disclosed that it would no longer seek new investment opportunities in marine assets within the Portfolio Management segment, but was committed to maximizing the value of existing investments. During the third quarter of 2015, GATX management made the decision to exit the majority of our marine investments within the Portfolio Management segment, including six chemical parcel tankers (the "Nordic Vessels"), most of the inland marine vessels and our 50% interest in the Cardinal Marine joint venture. As such, the Nordic Vessels and the inland marine vessels have been classified as held for sale and adjusted to the lower of their respective carrying amounts or fair value less costs to dispose. Furthermore, the Cardinal Marine joint venture was evaluated to assess whether an other-than-temporary decline in the value of the investment had occurred. As a result, an aggregate impairment loss of $49.8 million was recognized for certain of the vessels to be sold and the investment in the Cardinal Marine joint venture. These impairments were driven by our decision to exit these investments and resulted from the associated change in our expected use and holding periods for these assets. The impairment losses on the vessels ($30.8 million) were reported in net (loss) gains on asset dispositions, and the impairment loss on the investment in the Cardinal Marine joint venture ($19.0 million) was reported in the share of affiliates' earnings in the statement of comprehensive income. The fair value of the impaired assets at September 30, 2015 was $39.7 million for vessels and $25.2 million for our investment in the Cardinal Marine joint venture. We based the fair values of these assets on our estimate of the expected sales proceeds. The Portfolio Management marine investments sold during the third quarter of 2015 yielded proceeds of $31.6 million, resulting in a gain of $7.3 million. The remainder of the investments are expected to be sold by the end of fiscal year 2015. As of September 30, 2015, the Company had $175.0 million of assets classified as held for sale, primarily related to the marine vessels in the Portfolio Management segment. These investments are included in other assets on the balance sheet.

NOTE 5. Asset Impairments

GATX previously disclosed that it would no longer seek new investment opportunities in marine assets within the Portfolio Management segment, but was committed to maximizing the value of existing investments. During the third quarter of 2015, GATX management made the decision to exit the majority of our marine investments within the Portfolio Management segment, including six chemical parcel tankers (the "Nordic Vessels"), most of the inland marine vessels and our 50% interest in the Cardinal Marine joint venture. As such, the Nordic Vessels and the inland marine vessels have been classified as held for sale and adjusted to the lower of their respective carrying amounts or fair value less costs to dispose. Furthermore, the Cardinal Marine joint venture was evaluated to assess whether an other-than-temporary decline in the value of the investment had occurred. As a result, an aggregate impairment loss of $49.8 million was recognized for certain of the vessels to be sold and the investment in the Cardinal Marine joint venture. These impairments were driven by our decision to exit these investments and resulted from the associated change in our expected use and holding periods for these assets. The impairment losses on the vessels ($30.8 million) were reported in net (loss) gains on asset dispositions, and the impairment loss on the investment in the Cardinal Marine joint venture ($19.0 million) was reported in the share of affiliates' earnings in the statement of comprehensive income. The fair value of the impaired assets at September 30, 2015 was $39.7 million for vessels and $25.2 million for our investment in the Cardinal Marine joint venture. We based the fair values of these assets on our estimate of the expected sales proceeds.

The Portfolio Management marine investments sold during the third quarter of 2015 yielded proceeds of $31.6 million, resulting in a gain of $7.3 million. The remainder of the investments are expected to be sold by the end of fiscal year 2015. As of September 30, 2015, the Company had $175.0 million of assets classified as held for sale, primarily related to the marine vessels in the Portfolio Management segment. These investments are included in other assets on the balance sheet.