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Shareholders' Equity (Details 4) (USD $) | 12 Months Ended | 1 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2014 | May 31, 2014
Information by exercise price range |  |  |  |
Options Outstanding, Number Outstanding (in shares) | 1,255,077 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions |  | 1,255,077 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions |
Options Outstanding, Weighted Average Remaining Contractual Life | 7 years 3 months 15 days |  |  |
Options Outstanding, Weighted Average Exercise Price Per Share | $ 2.86 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1 |  | $ 2.86 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1 |
Options Exercisable, Number Exercisable (in shares) | 710,598 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions | 686,998 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions | 710,598 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions |
Options Exercisable, Weighted Average Exercise Price Per Share | $ 3.01 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1 |  | $ 3.01 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1 |
Stock option disclosures |  |  |  |
Aggregate intrinsic value of options outstanding (in dollars) | $ 1,186,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue |  | $ 1,186,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue |
Weighted average remaining life of options exercisable | 6 years 4 days |  |  |
Aggregate intrinsic value of options exercisable (in dollars) | 685,000 us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1 |  | 685,000 us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1 |
Weighted average grant-date fair value of options granted (in dollars per share) | $ 1.13 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue | $ 1.01 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue |  |
Total number of shares granted to the Board of directors (in shares) | 29,701 isig_ShareBasedCompensationArrangementByShareBasedPaymentAwardStockAwardsGranted | 39,032 isig_ShareBasedCompensationArrangementByShareBasedPaymentAwardStockAwardsGranted |  |
Restricted stock units granted (in shares) | 25,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod |  |  |
Restricted stock units |  |  |  |
Stock option disclosures |  |  |  |
Vesting period |  |  |  | 3 years
Restricted stock units granted (in shares) | 25,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |  |  |
Fair value of units |  |  | $ 3.03 isig_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |
$1.61 - $2.46 |  |  |  |
Information by exercise price range |  |  |  |
Ranges of Exercise Prices, Lower (in dollars per share) | $ 1.61 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeOneMember |  |  |
Ranges of Exercise Prices, Upper (in dollars per share) | $ 2.46 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeOneMember |  |  |
Options Outstanding, Number Outstanding (in shares) | 532,831 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeOneMember |  | 532,831 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeOneMember |
Options Outstanding, Weighted Average Remaining Contractual Life | 7 years 4 months 24 days |  |  |
Options Outstanding, Weighted Average Exercise Price Per Share | $ 1.85 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeOneMember |  | $ 1.85 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeOneMember |
Options Exercisable, Number Exercisable (in shares) | 351,852 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeOneMember |  | 351,852 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeOneMember |
Options Exercisable, Weighted Average Exercise Price Per Share | $ 1.80 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeOneMember |  | $ 1.80 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeOneMember |
$2.79 - $4.22 |  |  |  |
Information by exercise price range |  |  |  |
Ranges of Exercise Prices, Lower (in dollars per share) | $ 2.79 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeTwoMember |  |  |
Ranges of Exercise Prices, Upper (in dollars per share) | $ 4.22 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeTwoMember |  |  |
Options Outstanding, Number Outstanding (in shares) | 621,246 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeTwoMember |  | 621,246 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeTwoMember |
Options Outstanding, Weighted Average Remaining Contractual Life | 7 years 9 months 4 days |  |  |
Options Outstanding, Weighted Average Exercise Price Per Share | $ 3.30 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeTwoMember |  | $ 3.30 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeTwoMember |
Options Exercisable, Number Exercisable (in shares) | 257,746 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeTwoMember |  | 257,746 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeTwoMember |
Options Exercisable, Weighted Average Exercise Price Per Share | $ 3.69 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeTwoMember |  | $ 3.69 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceRangeTwoMember |
$5.49 |  |  |  |
Information by exercise price range |  |  |  |
Exercise price (in dollars per share) | $ 5.49 isig_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePrice / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceMember |  |  |
Options Outstanding, Number Outstanding (in shares) | 101,000 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceMember |  | 101,000 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceMember |
Options Outstanding, Weighted Average Remaining Contractual Life | 3 years 10 months 13 days |  |  |
Options Outstanding, Weighted Average Exercise Price Per Share | $ 5.49 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceMember |  | $ 5.49 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceMember |
Options Exercisable, Number Exercisable (in shares) | 101,000 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceMember |  | 101,000 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceMember |
Options Exercisable, Weighted Average Exercise Price Per Share | $ 5.49 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceMember |  | $ 5.49 us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1 / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = isig_ExercisePriceMember |
2013 Plan |  |  |  |
Stock option disclosures |  |  |  |
Total number of shares granted to the Board of directors (in shares) | 29,701 isig_ShareBasedCompensationArrangementByShareBasedPaymentAwardStockAwardsGranted / us-gaap_PlanNameAxis = isig_StockOptionPlan2013Member | 39,032 isig_ShareBasedCompensationArrangementByShareBasedPaymentAwardStockAwardsGranted / us-gaap_PlanNameAxis = isig_StockOptionPlan2013Member |  |
Shares issue price (in dollars per share) | $ 3.03 us-gaap_SharePrice / us-gaap_PlanNameAxis = isig_StockOptionPlan2013Member | $ 2.69 us-gaap_SharePrice / us-gaap_PlanNameAxis = isig_StockOptionPlan2013Member | $ 3.03 us-gaap_SharePrice / us-gaap_PlanNameAxis = isig_StockOptionPlan2013Member |
Total value of shares issued | $ 90,000 us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation / us-gaap_PlanNameAxis = isig_StockOptionPlan2013Member | $ 105,000 us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation / us-gaap_PlanNameAxis = isig_StockOptionPlan2013Member |  |

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