XML 87 R73.htm IDEA: XBRL DOCUMENT
v3.20.4

Stock-Based Compensation - Additional Information (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of shares available for grant | 4,400,000 |  |
Common stock, par value (in dollars per share) | $ 0.0005 | $ 0.0005 |
Total share-based compensation cost not yet recognized | $ 84,600,000 |  |
Remaining weighted average service period | 2 years 4 months 24 days |  |
Proceeds from employee stock purchase plan | $ 18,085,000 | $ 17,629,000 | $ 14,689,000
Employee Stock Purchase Plan |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Employee stock purchase plan, stock purchases as a percentage of employee compensation, maximum | 10.00% |  |
Maximum share value authorized for purchase under employee stock purchase plan | $ 23,750 |  |
Exercisable price percentage of closing price of another class of stock | 95.00% |  |
Maximum number of shares that may be purchased by eligible participants | 400,000 |  |
Proceeds from employee stock purchase plan | $ 18,100,000 | $ 17,600,000 | $ 14,700,000
Stock appreciation rights |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Remaining weighted average service period | 6 years 1 month 6 days |  |
Award vesting period | 4 years |  |
Award expiry period from date of grant | 7 years |  |
Total compensation cost not yet recognized, period for recognition | 4 years |  |
Restricted stock units | Service-based Awards |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Award vesting period | 4 years |  |
Restricted stock units | Performance Shares |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Award vesting period | 4 years |  |
CSEs |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Base fee percentage | 50.00% |  |

X
- Definition Base fee percentage. + References No definition available. + Details
Name: | it_BaseFeePercentage
Namespace Prefix: | it_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Employee Stock Purchase Plan Maximum Number of Shares that May be Purchase by Eligible Participants + References No definition available. + Details
Name: | it_EmployeeStockPurchasePlanMaximumNumberofSharesthatMaybePurchasebyEligibleParticipants
Namespace Prefix: | it_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share Based Compensation Arrangement By Employee Stock Purchase Plan Stock Purchases as Percentage Of Employee Compensation Maximum. + References No definition available. + Details
Name: | it_ShareBasedCompensationArrangementByEmployeeStockPurchasePlanStockPurchasesAsPercentageOfEmployeeCompensationMaximum
Namespace Prefix: | it_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share based Compensation Arrangement by Share based Payment Award, Equity Instruments Other than Options, Granted in Period, Weighted Average Remaining Contractual Term. + References No definition available. + Details
Name: | it_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedInPeriodWeightedAverageRemainingContractualTerm
Namespace Prefix: | it_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share Based Compensation Arrangement By Share Based Payment Award Exercisable Price Percentage Of Closing Price Of Another Class Of Stock. + References No definition available. + Details
Name: | it_ShareBasedCompensationArrangementByShareBasedPaymentAwardExercisablePricePercentageOfClosingPriceOfAnotherClassOfStock
Namespace Prefix: | it_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share based compensation arrangement by share based payment award expiry period from date of grant. + References No definition available. + Details
Name: | it_ShareBasedCompensationArrangementByShareBasedPaymentAwardExpiryPeriodFromDateOfGrant
Namespace Prefix: | it_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share Based Compensation Arrangement By Share Based Payment Award Maximum Share Value Authorized For Purchase Under Employee Stock Purchase Plan. + References No definition available. + Details
Name: | it_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumShareValueAuthorizedForPurchaseUnderEmployeeStockPurchasePlan
Namespace Prefix: | it_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Face amount or stated value per share of common stock. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of cost not yet recognized for nonvested award under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of cash inflow from issuance of shares under share-based payment arrangement. Includes, but is not limited to, option exercised. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120381028&loc=SL79508275-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585 + Details
Name: | us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares authorized for issuance under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_PlanNameAxis=it_EmployeeStockPurchasePlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_StockAppreciationRightsSARSMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | it_RestrictedEquityAwardTypeAxis=it_ServiceBasedAwardsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | it_RestrictedEquityAwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=it_CommonStockEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |