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Note 16 - Employee Benefit Plans (Details) - Weighted Average Asset Allocations
12 Months Ended
Dec. 28, 2014
Dec. 29, 2013
Asset Category:    
Target allocation 100.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations  
Percentage of plan assets at year end 100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations 100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Equity Securities [Member] | Minimum [Member]    
Asset Category:    
Target allocation 55.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Equity Securities [Member] | Maximum [Member]    
Asset Category:    
Target allocation 65.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Equity Securities [Member]    
Asset Category:    
Percentage of plan assets at year end 63.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquitySecuritiesMember
65.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquitySecuritiesMember
Debt Securities [Member] | Minimum [Member]    
Asset Category:    
Target allocation 30.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Debt Securities [Member] | Maximum [Member]    
Asset Category:    
Target allocation 40.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Debt Securities [Member]    
Asset Category:    
Percentage of plan assets at year end 34.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
32.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
Other Securities [Member] | Minimum [Member]    
Asset Category:    
Target allocation 0.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= tile_OtherSecuritiesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Other Securities [Member] | Maximum [Member]    
Asset Category:    
Target allocation 5.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= tile_OtherSecuritiesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Other Securities [Member]    
Asset Category:    
Percentage of plan assets at year end 3.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= tile_OtherSecuritiesMember
3.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= tile_OtherSecuritiesMember