XML 31 R53.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Business and Summary of Significant Accounting Policies and Estimates - Goodwill (Details) | 12 Months Ended
--- | ---
Dec. 31, 2019 geographic_region
Accounting Policies [Abstract] |
Number of geographic regions | 3

X
- Definition Number of geographic regions + References No definition available. + Details
Name: | gpi_NumberOfGeographicRegions
Namespace Prefix: | gpi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration