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Consolidated Statement of Stockholders' Equity (Parenthetical) | 3 Months Ended
--- | ---
Jun. 30, 2014
3.00% Convertible Notes [Member] |
Convertible senior notes stated rate | 3.00%
2.25% Convertible Notes [Member] |
Convertible senior notes stated rate | 2.25%

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- Definition Equity component convertible note rate. + References No definition available. + Details
Name: | gpi_EquityComponentConvertibleNoteRate
Namespace Prefix: | gpi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration