XML 104 R48.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Shareholders' Equity (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2014
Stockholders' Equity Note [Abstract] |
Common stock reserved for conversion and incentive plans | The following shares of common stock were reserved as of December 31, 2014 (in millions):
GATX Corporation 2004 Equity Incentive Compensation Plan | 2.5 |
GATX Corporation 2012 Incentive Award Plan | 3.5 |
| 6.0 |

X
- Definition Common stock reserved for conversion and incentive plans. + References No definition available. + Details
Name: | gmt_CommonStockReservedForConversionAndIncentivePlansTableTextBlock
Namespace Prefix: | gmt_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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