Organization and Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2017
Accounting Policies [Abstract]
Organization and Summary of Significant Accounting Policies	NOTE 1. ORGANIZATION & SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Unless the context requires otherwise, the terms “we,” “us,” “our,” or “our Company” are used to mean The Navigators Group, Inc., a Delaware holding company established in 1982, and its subsidiaries. The term “Parent Company” is used to mean The Navigators Group, Inc. without its subsidiaries. Organization We are an international insurance company with a long-standing area of specialization in Marine insurance. We also offer Property and Casualty (“P&C”) insurance, primarily general liability coverage and umbrella & excess liability coverage to commercial enterprises through our Primary and Excess Casualty divisions. We have also developed niches in Professional Liability insurance, through our Directors & Officers (“D&O”) and Errors & Omissions (“E&O”) divisions, as well as assumed reinsurance products. We operate through various wholly-owned insurance and service companies. Our subsidiaries domiciled in the United States (“U.S.”) include two insurance companies, Navigators Insurance Company (“NIC”) and Navigators Specialty Insurance Company (“NSIC”), as well as our U.S. underwriting agency, Navigators Management Company (“NMC”). NIC includes a branch in the United Kingdom (“U.K”). We also have operations domiciled in the U.K., Belgium, Hong Kong and throughout Europe. Navigators International Insurance Company Ltd. (“NIIC”), Navigators Management (U.K.) Ltd. (“NMUK”) and Navigators Underwriting Ltd. (“NUL”) are domiciled in the U.K. and NUL includes European branches. Navigators Underwriting Agency Ltd. (“NUAL”), a Lloyd’s of London (“Lloyd’s”) underwriting agency, manages and provides the capital, through Navigators Corporate Underwriters Ltd. (“NCUL”), for our Lloyd’s Syndicate 1221 (the “Syndicate”), and is also domiciled in the U.K. We control 100% of the Syndicate’s stamp capacity. Effective January 1, 2017, we sold our underwriting agency operations in Sweden and Denmark. The transaction represented a 100% disposition of our Sweden and Denmark corporations, NUAL AB and Navigators A/S, respectively. This transaction did not have a material impact on our financial statements. Basis of Presentation The Consolidated Balance Sheet at March 31, 2017 and the Consolidated Statements of Income, Comprehensive Income, Stockholders’ Equity and Cash Flows for the periods ended March 31, 2017 and 2016 are unaudited. The Balance Sheet at December 31, 2016 is derived from our audited Financial Statements. The accompanying Interim Consolidated Financial Statements reflect all adjustments, which, in the opinion of management, are necessary to fairly present the results of The Navigators Group, Inc. and its subsidiaries for the interim periods presented on the basis of United States generally accepted accounting principles (“GAAP” or “U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X as promulgated by the U.S. Securities and Exchange Commission. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. All significant intercompany transactions and balances have been eliminated in consolidation. The preparation of these Financial Statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the Financial Statements and the reported revenues and expenses during the reporting periods. The results of operations for any interim period are not necessarily indicative of results for the full year. The Interim Consolidated Financial Statements should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2016. Certain amounts for the prior period have been reclassified to conform with the current period presentation. Income Taxes The interim income tax provision has been computed based on our estimated annual Effective tax rate, which represents our best estimate on a year to date basis for the interim period. As a result, the tax provision for a given quarter equals the difference between the provision recorded cumulatively year to date less the amount recorded cumulatively as of the end of the prior interim period. Our Effective tax rate for the quarter and year to date differs from the federal tax rate of 35% primarily due to an excess tax benefit related to the vesting of stock compensation at fair market value, tax-exempt investment income and dividends received deduction. In the first quarter of 2017, excess tax benefits related to the vesting of stock compensation was recognized as a reduction to Income tax expense rather than as an increase to Additional paid-in capital as a result of the adoption of the Accounting Standards Update (“ASU”) 2016-09 (see section New Accounting Standards Adopted in 2017 of this footnote for further information on the adoption of this standard). Significant Accounting Policies There were no changes in our significant accounting policies subsequent to our Annual Report on Form 10-K for the year ended December 31, 2016. New Accounting Standards Adopted in 2017 Share-Based Compensation Accounting Effective January 1, 2017, our Company adopted ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting” issued by the Financial Accounting Standards Board (the “FASB”). This guidance requires all income tax effects of awards to be recognized in the income statement when the awards vest or are settled, eliminates the requirement that excess tax benefits be realized before companies can recognize them, requires the presentation of excess tax benefits as an operating activity on the statement of cash flows, allows employers to increase the amounts withheld to cover income taxes on share-based compensation awards without requiring liability classification, requires the presentation of employee taxes paid as a financing activity on the statement of cash flows, and requires companies to elect whether they will account for award forfeitures by recognizing forfeitures only as they occur or by estimating the number of awards expected to be forfeited. The requirement to recognize all income tax effects of awards in the income statement when the awards vest or are settled was adopted on a prospective basis. Previously, these amounts were recorded in Additional paid-in capital. This change also prospectively impacts the calculation of potential common shares used to determine Diluted net income per common share under the treasury stock method. The new standard requires that assumed proceeds under the treasury stock method be modified to exclude the amount of excess tax benefits that previously would have been recognized in Additional paid-in capital. We elected to account for forfeitures of share-based payment awards by recognizing forfeitures of awards as they occur, and upon adoption of this guidance, the payment of employee taxes was retrospectively adjusted on the Consolidated Statements of Cash Flows to be classified as a financing activity. All other changes in the ASU did not result in cumulative-effect or retrospective adjustments. The adoption of this guidance did not materially impact our results of operations, financial condition or liquidity. Transition to Equity Method of Accounting Effective January 1, 2017, our Company adopted the ASU 2016-07, “Simplifying the Transition to the Equity Method of Accounting” issued by the FASB. This guidance eliminates the requirement to retrospectively apply equity method accounting when an investment that had been accounted for by another method initially qualifies for the equity method. Our Company did not have any investments transitioning to the equity method of accounting during the three months ended March 31, 2017. The adoption of this guidance did not impact our results of operations, financial condition or liquidity. Recently Issued Accounting Standards Not Yet Adopted Definition of a Business In January 2017, the FASB issued ASU 2017-01, “Clarifying the Definition of a Business” with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. This guidance is effective for annual periods beginning after December 15, 2017, and interim periods within those fiscal years with early adoption permitted. This guidance will be applied prospectively to any transactions occurring within the period of adoption. Goodwill Impairment In January 2017, the FASB issued ASU 2017-04, “Simplifying the Test for Goodwill Impairment” that eliminates the requirement to calculate the implied fair value of goodwill (i.e., Step 2 of the current goodwill impairment test) to measure a goodwill impairment charge. Instead, an impairment charge will be based on the excess of a reporting unit’s carrying amount over its fair value (i.e., measure the charge based on Step 1 of the current goodwill impairment test). This guidance is effective for annual and interim impairment tests performed in periods beginning after December 15, 2019, with early adoption permitted for annual and interim goodwill impairment testing dates after January 1, 2017. This guidance will be adopted on a prospective basis. Callable Debt Securities In March 2017, the FASB issued ASU 2017-08, “Premium Amortization on Purchased Callable Debt Securities” that shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. This guidance is effective for annual periods beginning after December 15, 2018, and interim periods within those fiscal years with early adoption permitted. This guidance will be adopted using a modified retrospective transition approach. The adoption of this guidance is not expected to materially impact our results of operations, financial condition or liquidity.

NOTE 1. ORGANIZATION & SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Unless the context requires otherwise, the terms “we,” “us,” “our,” or “our Company” are used to mean The Navigators Group, Inc., a Delaware holding company established in 1982, and its subsidiaries. The term “Parent Company” is used to mean The Navigators Group, Inc. without its subsidiaries.

Organization

We are an international insurance company with a long-standing area of specialization in Marine insurance. We also offer Property and Casualty (“P&C”) insurance, primarily general liability coverage and umbrella & excess liability coverage to commercial enterprises through our Primary and Excess Casualty divisions. We have also developed niches in Professional Liability insurance, through our Directors & Officers (“D&O”) and Errors & Omissions (“E&O”) divisions, as well as assumed reinsurance products.

We operate through various wholly-owned insurance and service companies. Our subsidiaries domiciled in the United States (“U.S.”) include two insurance companies, Navigators Insurance Company (“NIC”) and Navigators Specialty Insurance Company (“NSIC”), as well as our U.S. underwriting agency, Navigators Management Company (“NMC”). NIC includes a branch in the United Kingdom (“U.K”). We also have operations domiciled in the U.K., Belgium, Hong Kong and throughout Europe. Navigators International Insurance Company Ltd. (“NIIC”), Navigators Management (U.K.) Ltd. (“NMUK”) and Navigators Underwriting Ltd. (“NUL”) are domiciled in the U.K. and NUL includes European branches. Navigators Underwriting Agency Ltd. (“NUAL”), a Lloyd’s of London (“Lloyd’s”) underwriting agency, manages and provides the capital, through Navigators Corporate Underwriters Ltd. (“NCUL”), for our Lloyd’s Syndicate 1221 (the “Syndicate”), and is also domiciled in the U.K. We control 100% of the Syndicate’s stamp capacity.

Effective January 1, 2017, we sold our underwriting agency operations in Sweden and Denmark. The transaction represented a 100% disposition of our Sweden and Denmark corporations, NUAL AB and Navigators A/S, respectively. This transaction did not have a material impact on our financial statements.

Basis of Presentation

The Consolidated Balance Sheet at March 31, 2017 and the Consolidated Statements of Income, Comprehensive Income, Stockholders’ Equity and Cash Flows for the periods ended March 31, 2017 and 2016 are unaudited. The Balance Sheet at December 31, 2016 is derived from our audited Financial Statements. The accompanying Interim Consolidated Financial Statements reflect all adjustments, which, in the opinion of management, are necessary to fairly present the results of The Navigators Group, Inc. and its subsidiaries for the interim periods presented on the basis of United States generally accepted accounting principles (“GAAP” or “U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X as promulgated by the U.S. Securities and Exchange Commission. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. All significant intercompany transactions and balances have been eliminated in consolidation. The preparation of these Financial Statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the Financial Statements and the reported revenues and expenses during the reporting periods. The results of operations for any interim period are not necessarily indicative of results for the full year. The Interim Consolidated Financial Statements should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2016. Certain amounts for the prior period have been reclassified to conform with the current period presentation.

Income Taxes

The interim income tax provision has been computed based on our estimated annual Effective tax rate, which represents our best estimate on a year to date basis for the interim period. As a result, the tax provision for a given quarter equals the difference between the provision recorded cumulatively year to date less the amount recorded cumulatively as of the end of the prior interim period. Our Effective tax rate for the quarter and year to date differs from the federal tax rate of 35% primarily due to an excess tax benefit related to the vesting of stock compensation at fair market value, tax-exempt investment income and dividends received deduction.

In the first quarter of 2017, excess tax benefits related to the vesting of stock compensation was recognized as a reduction to Income tax expense rather than as an increase to Additional paid-in capital as a result of the adoption of the Accounting Standards Update (“ASU”) 2016-09 (see section New Accounting Standards Adopted in 2017 of this footnote for further information on the adoption of this standard).

Significant Accounting Policies

There were no changes in our significant accounting policies subsequent to our Annual Report on Form 10-K for the year ended December 31, 2016.

New Accounting Standards Adopted in 2017

Share-Based Compensation Accounting

Effective January 1, 2017, our Company adopted ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting” issued by the Financial Accounting Standards Board (the “FASB”). This guidance requires all income tax effects of awards to be recognized in the income statement when the awards vest or are settled, eliminates the requirement that excess tax benefits be realized before companies can recognize them, requires the presentation of excess tax benefits as an operating activity on the statement of cash flows, allows employers to increase the amounts withheld to cover income taxes on share-based compensation awards without requiring liability classification, requires the presentation of employee taxes paid as a financing activity on the statement of cash flows, and requires companies to elect whether they will account for award forfeitures by recognizing forfeitures only as they occur or by estimating the number of awards expected to be forfeited.

The requirement to recognize all income tax effects of awards in the income statement when the awards vest or are settled was adopted on a prospective basis. Previously, these amounts were recorded in Additional paid-in capital. This change also prospectively impacts the calculation of potential common shares used to determine Diluted net income per common share under the treasury stock method. The new standard requires that assumed proceeds under the treasury stock method be modified to exclude the amount of excess tax benefits that previously would have been recognized in Additional paid-in capital.

We elected to account for forfeitures of share-based payment awards by recognizing forfeitures of awards as they occur, and upon adoption of this guidance, the payment of employee taxes was retrospectively adjusted on the Consolidated Statements of Cash Flows to be classified as a financing activity. All other changes in the ASU did not result in cumulative-effect or retrospective adjustments. The adoption of this guidance did not materially impact our results of operations, financial condition or liquidity.

Transition to Equity Method of Accounting

Effective January 1, 2017, our Company adopted the ASU 2016-07, “Simplifying the Transition to the Equity Method of Accounting” issued by the FASB. This guidance eliminates the requirement to retrospectively apply equity method accounting when an investment that had been accounted for by another method initially qualifies for the equity method. Our Company did not have any investments transitioning to the equity method of accounting during the three months ended March 31, 2017. The adoption of this guidance did not impact our results of operations, financial condition or liquidity.

Recently Issued Accounting Standards Not Yet Adopted

Definition of a Business

In January 2017, the FASB issued ASU 2017-01, “Clarifying the Definition of a Business” with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. This guidance is effective for annual periods beginning after December 15, 2017, and interim periods within those fiscal years with early adoption permitted. This guidance will be applied prospectively to any transactions occurring within the period of adoption.

Goodwill Impairment

In January 2017, the FASB issued ASU 2017-04, “Simplifying the Test for Goodwill Impairment” that eliminates the requirement to calculate the implied fair value of goodwill (i.e., Step 2 of the current goodwill impairment test) to measure a goodwill impairment charge. Instead, an impairment charge will be based on the excess of a reporting unit’s carrying amount over its fair value (i.e., measure the charge based on Step 1 of the current goodwill impairment test). This guidance is effective for annual and interim impairment tests performed in periods beginning after December 15, 2019, with early adoption permitted for annual and interim goodwill impairment testing dates after January 1, 2017. This guidance will be adopted on a prospective basis.

Callable Debt Securities

In March 2017, the FASB issued ASU 2017-08, “Premium Amortization on Purchased Callable Debt Securities” that shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. This guidance is effective for annual periods beginning after December 15, 2018, and interim periods within those fiscal years with early adoption permitted. This guidance will be adopted using a modified retrospective transition approach. The adoption of this guidance is not expected to materially impact our results of operations, financial condition or liquidity.