No definition available.

Name:	gdi_ChangesInTheValueOfDebtAndDesignatedInterestRateSwapsAbstract
Namespace Prefix:	gdi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that of income tax was recognized in other comprehensive income during the current period.

+ References

No definition available.

+ Details

Name:	gdi_DerivativeInstrumentsGainLossOfIncomeTaxRecordedInOtherComprehensiveIncome
Namespace Prefix:	gdi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e637-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e681-108580

+ Details

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

- Definition

Amount of hedged item in hedging relationship. Excludes hedged asset or liability.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeAmountOfHedgedItem
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

+ Details

Name:	us-gaap_DerivativeNumberOfInstrumentsHeld
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=gdi_TermLoanDenominatedInEurosDue2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CrossCurrencyInterestRateContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Hedging Activities and Fair Value Measurements, Investment in Consolidated Subsidiaries with Functional Currencies Other than USD (Details) € in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) Contract	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Contract	Sep. 30, 2017 USD ($)	Sep. 30, 2018 EUR (€) Contract	Aug. 17, 2017 EUR (€)	Aug. 16, 2017 USD ($) Contract
Derivative, Fair Value, Net [Abstract]
Number of contracts \| Contract	2		2		2
Euro Term Loan Due in 2020 [Member]
Derivative, Fair Value, Net [Abstract]
Long-term debt hedged \| €					€ 608.9	€ 615.0
Cross Currency Interest Rate Swap Contracts [Member]
Derivative, Fair Value, Net [Abstract]
Number of contracts \| Contract							2
Notional amount \| $							$ 100.0
Interest Rate Swap Contracts [Member]
Derivative, Fair Value, Net [Abstract]
Number of contracts \| Contract	11		11		11
Changes in the value of debt and designated interest rate swaps [Abstract]
Gain (loss), net of income tax, recorded through other comprehensive income \| $	$ 3.5	$ (13.6)	$ 18.0	$ (43.2)
Balance included in accumulated other comprehensive (loss) income as of September 30, 2018 and 2017, respectively \| $	$ 50.1	$ 39.2	$ 50.1	$ 39.2