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Note 6 - Employee Benefit Plans (Details) - Net Periodic Benefit Cost (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 05, 2015	Mar. 30, 2014
Defined Benefit Retirement Plan (Europe) [Member]
Note 6 - Employee Benefit Plans (Details) - Net Periodic Benefit Cost [Line Items]
Service cost	$ 269us-gaap_DefinedBenefitPlanServiceCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember	$ 175us-gaap_DefinedBenefitPlanServiceCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember
Interest cost	2,093us-gaap_DefinedBenefitPlanInterestCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember	2,515us-gaap_DefinedBenefitPlanInterestCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember
Expected return on assets	(2,247)us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember	(2,825)us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember
Amortization of prior service costs	8us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember	12us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember
Recognized net actuarial (gains)/losses	239us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember	153us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember
Net periodic benefit cost	362us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember	30us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_DefinedBenefitRetirementPlanEuropeMember
Salary Continuation Plan (SCP) [Member]
Note 6 - Employee Benefit Plans (Details) - Net Periodic Benefit Cost [Line Items]
Service cost	148us-gaap_DefinedBenefitPlanServiceCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_SalaryContinuationPlanSCPMember	125us-gaap_DefinedBenefitPlanServiceCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_SalaryContinuationPlanSCPMember
Interest cost	278us-gaap_DefinedBenefitPlanInterestCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_SalaryContinuationPlanSCPMember	268us-gaap_DefinedBenefitPlanInterestCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_SalaryContinuationPlanSCPMember
Amortization of prior service costs	0us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_SalaryContinuationPlanSCPMember	6us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_SalaryContinuationPlanSCPMember
Amortization of (gain)/loss	131us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_SalaryContinuationPlanSCPMember	67us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_SalaryContinuationPlanSCPMember
Net periodic benefit cost	$ 557us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_SalaryContinuationPlanSCPMember	$ 466us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = tile_SalaryContinuationPlanSCPMember

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Namespace Prefix:	tile_
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X

- Definition

The amount of gains or losses recognized in net periodic benefit cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(4)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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X

- Definition

The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Prior Service Cost

-URI http://asc.fasb.org/extlink&oid=49177896



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(1)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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- Definition

Amount before tax, after reclassification adjustments, of actuarial gain (loss) that has not been recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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- Definition

An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Expected Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512171



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(3)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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- Definition

The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(2)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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X

- Definition

The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (j)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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X

- Definition

The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(1)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Service Cost (Component of Net Periodic Pension Cost)

-URI http://asc.fasb.org/extlink&oid=6525008



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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