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v3.8.0.1

Debt - Instruments (Details) - USD ($) |  | 12 Months Ended |
--- | --- | --- | ---
Jan. 30, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Amended credit facility | Subsequent event |  |  |
Debt |  |  |
Payment on outstanding amounts owed | $ 300,000,000.0 |  |
Amended credit facility | Subsequent event | Credit facility |  |  |
Debt |  |  |
Maximum borrowing capacity | $ 1,160,000,000 |  |
Credit facility |  |  |
Debt |  |  |
Maximum borrowing capacity |  | $ 1,260,000,000 |
Maximum additional borrowings available at the entity's request subject to satisfaction of certain conditions |  | 200,000,000.0 |
Amount outstanding |  | 60,000,000.0 | $ 325,200,000
Unused portion of facility |  | $ 1,190,000,000 | 926,500,000
Commitment fee on the unused portion of the credit facility |  | 0.35% |
Credit facility | Base rate |  |  |
Debt |  |  |
Reference rate for variable rate of interest |  | base rate |
Credit facility | Eurodollar |  |  |
Debt |  |  |
Reference rate for variable rate of interest |  | Eurodollar rate |
Letters of credit and bankers' acceptances |  |  |
Debt |  |  |
Maximum borrowing capacity |  | $ 400,000,000.0 |
Amount outstanding |  | $ 8,600,000 | 8,300,000
Letters of credit fees (as a percent) |  | 0.25% |
Term loans |  |  |
Debt |  |  |
Amount of term loan outstanding |  | $ 835,800,000 | 840,000,000.0
Term loans | Base rate |  |  |
Debt |  |  |
Basis points added to reference rate |  | 1.50% |
Term loans | Eurodollar |  |  |
Debt |  |  |
Basis points added to reference rate |  | 2.50% |
Other uncommitted credit lines |  |  |
Debt |  |  |
Letters of credit, outstanding amount |  | $ 272,000,000.0 | $ 176,500,000

X
- Definition Maximum additional borrowing capacity available under the credit facility at the entity's request subject to satisfaction of certain conditions. + References No definition available. + Details
Name: | int_LineOfCreditFacilityMaximumAdditionalBorrowingCapacity
Namespace Prefix: | int_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
Period Type: | duration

X
- Definition The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR. + References No definition available. + Details
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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
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Period Type: | duration

X
- Definition Represents the aggregate of total long-term debt, including current maturities and short-term debt. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
Period Type: | duration

X
- Definition Fair value of the amount outstanding under the credit facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13476-108611 + Details
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Period Type: | instant

X
- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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Period Type: | instant

X
- Definition Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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X
- Definition The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility. + References No definition available. + Details
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- Definition The cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585 + Details
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- Details
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