XML 79 R63.htm IDEA: XBRL DOCUMENT v3.10.0.1

Summary of Significant Accounting Policies and Estimates - Adoption of Topic 606, "Revenue from Contracts with Customers" (Details) $ in Thousands	Jan. 01, 2018 USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect adjustments to retained earnings	$ 11,397
ASU 2014-09 | Adjustment due to Topic 606 | Maintenance and Repair Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect adjustments to retained earnings	4,800
ASU 2014-09 | Adjustment due to Topic 606 | Vehicle Financing, Sale of Service, and Other Insurance Contracts
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cumulative effect adjustments to retained earnings	$ 6,600

X

- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

+ References

No definition available.

+ Details

Name:	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201409Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis=us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ProductOrServiceAxis=gpi_MaintenanceAndRepairMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_FinancialServiceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: