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Employee Stock Purchase Plan - Additional Information (Detail) (Totals, USD $) In Millions, except Share data, unless otherwise specified | 3 Months Ended |
--- | --- | ---
Mar. 31, 2015 | Aug. 16, 2014
Totals |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Percentage of lower limit value of common stock | 85.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent / us-gaap_AwardTypeAxis = nvtl_EmployeeStockPurchasePlansMember |
Maximum limit of payroll deductions (percent) | 10.00%us-gaap_DeferredCompensationArrangementWithIndividualCashAwardsGrantedPercentage / us-gaap_AwardTypeAxis = nvtl_EmployeeStockPurchasePlansMember |
Number of shares issue that the ESPP authorizes for purchase by eligible employees |  | 1,500,132 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_AwardTypeAxis = nvtl_EmployeeStockPurchasePlansMember
Total fair value of awards recognized as expenses | $ 0.1 us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1 / us-gaap_AwardTypeAxis = nvtl_EmployeeStockPurchasePlansMember |

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- Definition Commitment made to pay deferred cash remuneration expressed as a percentage of the individual's base salary. + References No definition available. + Details
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- Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Purchase price of common stock expressed as a percentage of its fair value. + References No definition available. + Details
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