Number of Nonoperating Segments

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- Definition

Percentage Control of Stamp Capacity

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- Definition

Navigators Specialty is 100% reinsured by Navigators Insurance Company.

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 20

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Carrying amount of finite-lived intangible assets, indefinite-lived intangible assets and goodwill. Goodwill is an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Intangible assets are assets, not including financial assets, lacking physical substance.

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Amount before tax of reclassification adjustment from accumulated other comprehensive income for translation gain (loss) realized upon the sale or liquidation of an investment in a foreign entity and foreign currency hedges that are designated and qualified as hedging instruments for hedges of the foreign currency exposure of a net investment in a foreign operation.

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 45

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-Name Accounting Standards Codification

-Topic 830

-SubTopic 30

-Section 45

-Paragraph 20

-Subparagraph (d)

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Amount after tax of reclassification adjustment from accumulated other comprehensive income for translation gain (loss) realized upon the sale or liquidation of an investment in a foreign entity and foreign currency hedges that are designated and qualified as hedging instruments for hedges of the foreign currency exposure of a net investment in a foreign operation.

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The net carrying amount as of the balance sheet date of other indefinite-lived and finite-lived intangible assets that are not separately presented on the statement of financial position.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Organization and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014 Segment	Dec. 31, 2013	Dec. 31, 2012
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of underwriting segments	2us-gaap_NumberOfOperatingSegments
Number of corporate segment	1navg_NumberOfNonoperatingSegments
Remeasurement of Foreign Currecy	$ 10,000,000
Remeasurement of Foreign currency, After tax	6,600,000
Goodwill and other intangible assets	7,013,000	7,177,000
Minimum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Maximum
Organization And Summary Of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	7 years
Navigators Insurance Company
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage of Navigators Specialty Insurance Company reinsured by Navigators Insurance Company	100.00%
Lloyd's
Organization And Summary Of Significant Accounting Policies [Line Items]
Goodwill	2,400,000	2,400,000
Other intangible assets	2,100,000	2,300,000
Lloyd's \| Syndicate 1221
Organization And Summary Of Significant Accounting Policies [Line Items]
Percentage control of stamp capacity	100.00%	100.00%	100.00%
Underwriting Segments
Organization And Summary Of Significant Accounting Policies [Line Items]
Goodwill	$ 2,500,000	$ 2,500,000