XML 30 R43.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Earnings Per Share (Details Textual) (USD $) In Millions, except Per Share data, unless otherwise specified | 3 Months Ended
--- | ---
Jun. 30, 2014
2.25% Convertible Notes [Member] |
Earnings Per Share (Textual) [Abstract] |
Debt interest rate | 2.25%
Dividend Threshold for Adjustment to Conversion Price | $ 0.14
2.25% Warrants [Member] |
Earnings Per Share (Textual) [Abstract] |
Debt interest rate | 2.25%
2.25% Purchased Options [Member] |
Earnings Per Share (Textual) [Abstract] |
Debt interest rate | 2.25%
3.00% Notes [Member] |
Earnings Per Share (Textual) [Abstract] |
Debt interest rate | 3.00%
3.00% Warrants [Member] |
Earnings Per Share (Textual) [Abstract] |
Debt interest rate | 3.00%
3.00% Purchased Options [Member] |
Earnings Per Share (Textual) [Abstract] |
Debt interest rate | 3.00%
3.00% Convertible Notes [Member] |
Earnings Per Share (Textual) [Abstract] |
Debt Instrument, Repurchased Face Amount | $ 92.5

X
- Definition Dividend threshold for adjustment to conversion price. + References No definition available. + Details
Name: | gpi_DividendThresholdForAdjustmentToConversionPrice
Namespace Prefix: | gpi_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | gpi_EarningsPerShareTextualAbstract
Namespace Prefix: | gpi_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Face (par) amount of the original debt instrument that was repurchased. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant