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Marketable Investments - Additional Information (Detail) (USD $) | 0 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Oct. 30, 2013 | Dec. 31, 2013 | Dec. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Auction rate securities par value |  | $ 80,988,000 us-gaap_AvailableForSaleSecuritiesAmortizedCost | $ 80,988,000 us-gaap_AvailableForSaleSecuritiesAmortizedCost |  |
ARS [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Auction rate securities par value |  | 11,000,000 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AuctionRateSecuritiesMember | 11,000,000 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AuctionRateSecuritiesMember |  |
Loss realized on ARS | 1,900,000 us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AuctionRateSecuritiesMember | 1,900,000 us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AuctionRateSecuritiesMember | 1,900,000 us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AuctionRateSecuritiesMember |  |
Proceeds from sale of ARS | $ 9,100,000 us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AuctionRateSecuritiesMember |  |  |  |
Minimum [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Intervals for each security |  |  |  | 7 days |
Interest rates on securities ranged |  |  | 0.10%invest_InvestmentInterestRate / us-gaap_RangeAxis = us-gaap_MinimumMember |  | 0.10%invest_InvestmentInterestRate / us-gaap_RangeAxis = us-gaap_MinimumMember
Maximum [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Intervals for each security |  |  |  | 35 days |
Interest rates on securities ranged |  |  | 0.40%invest_InvestmentInterestRate / us-gaap_RangeAxis = us-gaap_MaximumMember |  | 0.50%invest_InvestmentInterestRate / us-gaap_RangeAxis = us-gaap_MaximumMember

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- Definition Disclosure of the interest reset date intervals for level 3 financial assets. + References No definition available. + Details
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- Definition The interest rate for investments that have an interest rate. For fixed rate investments, this indicates the fixed interest rate. If the investment has a variable interest rate, the rate stated here may be the rate that is currently relevant. In this case the "Investment, Interest Rate is Current Rate for Variable Rate Investment Flag", "Investment, Interest Rate is Discount Rate at Purchase Flag", "Investment, Interest Rate Reflects Current Yield Flag" should be used. If one of these flags are not appropriate to explain the interest rate that is indicated, then a new flag should be added or an explanation should be included in "Investment, Additional Information". + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 12 -Sentence Column A + Details
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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + 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 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563 + Details
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- Details
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- Definition The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26853-111562 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 + Details
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