2.4.0.8100550 - Disclosure - Assumptions Used to Determine Fair Value of Stock Appreciation Rights Granted to Employees (Detail)truefalsefalse1false falsefalseC_0001085621_us-gaapAwardTypeAxis_us-gaapStockAppreciationRightsSARSMember_20120401_20120630http://www.sec.gov/CIK0001085621duration2012-04-01T00:00:002012-06-30T00:00:00U_pureStandardhttp://www.xbrl.org/2003/instancepure02false falsefalseC_0001085621_us-gaapAwardTypeAxis_us-gaapStockAppreciationRightsSARSMember_20120101_20120630http://www.sec.gov/CIK0001085621duration2012-01-01T00:00:002012-06-30T00:00:00U_pureStandardhttp://www.xbrl.org/2003/instancepure01false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse1false truefalseC_0001085621_us-gaapAwardTypeAxis_us-gaapStockAppreciationRightsSARSMember_20120401_20120630http://www.sec.gov/CIK0001085621duration2012-04-01T00:00:002012-06-30T00:00:00falsefalseSARsus-gaap_AwardTypeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_StockAppreciationRightsSARSMemberus-gaap_AwardTypeAxisexplicitMemberU_pureStandardhttp://www.xbrl.org/2003/instancepure0nanafalse0SARs2true 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]3false 5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.560.56falsefalsefalse2truetruefalse0.560.56falsefalsefalsenum:percentItemTypepureThe estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph e(2)(b) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false0Expected volatility4false 5us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1us-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse006 years 3 monthsfalsefalsefalse2falsefalsefalse006 years 3 monthsfalsefalsefalsexbrli:durationItemTypenaExpected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.D.2) -URI http://asc.fasb.org/extlink&oid=6793087&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section D -Subsection 2 false0Average expected life of SAR (in years)5false 5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.00920.0092falsefalsefalse2truetruefalse0.00920.0092falsefalsefalsenum:percentItemTypepureThe risk-free interest rate assumption that is used in valuing an option on its own shares.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iv) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph e(2)(d) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false0Risk-free interest rate6false 5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRateus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse00falsefalsefalse2truetruefalse00falsefalsefalsenum:percentItemTypepureThe estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph e(2)(c) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false0Dividend yieldfalseAssumptions Used to Determine Fair Value of Stock Appreciation Rights Granted to Employees (Detail) (SARs)UnKnownUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.icg.com/20130630/taxonomy/role/DisclosureAssumptionsUsedToDetermineFairValueOfStockAppreciationRightsGrantedToEmployeesDetail26