General	9 Months Ended
Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General	General Arch Capital Group Ltd. (“ACGL”) is a Bermuda public limited liability company which provides insurance and reinsurance on a worldwide basis through its subsidiaries (together with ACGL, the “Company”). On January 30, 2014, the Company acquired CMG Mortgage Insurance Company and its affiliated mortgage insurance companies (together, “CMG Entities”) and the mortgage insurance platform and related assets from PMI Mortgage Insurance Co. (“PMI”) (see Note 2). On March 20, 2014, the Company acquired approximately 11% of Watford Holdings Ltd.’s common equity and a warrant to purchase additional common equity for $100 million. Watford Holdings Ltd. is the parent of Watford Re Ltd., a newly-formed multi-line Bermuda reinsurance company (together with Watford Holdings Ltd., “Watford”). Watford is considered a variable interest entity (“VIE”) and the Company concluded that it is the primary beneficiary of Watford. As such, the results of Watford are included in the Company’s consolidated financial statements (see Note 4). The interim consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company and Watford. All significant intercompany transactions and balances have been eliminated in consolidation. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates and assumptions. In the opinion of management, the accompanying unaudited interim consolidated financial statements reflect all adjustments (consisting of normally recurring accruals) necessary for a fair statement of results on an interim basis. The results of any interim period are not necessarily indicative of the results for a full year or any future periods. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted; however, management believes that the disclosures are adequate to make the information presented not misleading. This report should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2013 (“2013 Form 10-K”), including the Company’s audited consolidated financial statements and related notes. The Company has reclassified the presentation of certain prior year information to conform to the current presentation. Such reclassifications had no effect on the Company’s net income, comprehensive income, shareholders’ equity or cash flows. Tabular amounts are in U.S. Dollars in thousands, except share amounts, unless otherwise noted.

General

9 Months Ended

Sep. 30, 2014

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Arch Capital Group Ltd. (“ACGL”) is a Bermuda public limited liability company which provides insurance and reinsurance on a worldwide basis through its subsidiaries (together with ACGL, the “Company”).

On January 30, 2014, the Company acquired CMG Mortgage Insurance Company and its affiliated mortgage insurance companies (together, “CMG Entities”) and the mortgage insurance platform and related assets from PMI Mortgage Insurance Co. (“PMI”) (see Note 2).

On March 20, 2014, the Company acquired approximately 11% of Watford Holdings Ltd.’s common equity and a warrant to purchase additional common equity for $100 million. Watford Holdings Ltd. is the parent of Watford Re Ltd., a newly-formed multi-line Bermuda reinsurance company (together with Watford Holdings Ltd., “Watford”). Watford is considered a variable interest entity (“VIE”) and the Company concluded that it is the primary beneficiary of Watford. As such, the results of Watford are included in the Company’s consolidated financial statements (see Note 4).

The interim consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company and Watford. All significant intercompany transactions and balances have been eliminated in consolidation. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates and assumptions. In the opinion of management, the accompanying unaudited interim consolidated financial statements reflect all adjustments (consisting of normally recurring accruals) necessary for a fair statement of results on an interim basis. The results of any interim period are not necessarily indicative of the results for a full year or any future periods.

Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted; however, management believes that the disclosures are adequate to make the information presented not misleading. This report should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2013 (“2013 Form 10-K”), including the Company’s audited consolidated financial statements and related notes.

The Company has reclassified the presentation of certain prior year information to conform to the current presentation. Such reclassifications had no effect on the Company’s net income, comprehensive income, shareholders’ equity or cash flows. Tabular amounts are in U.S. Dollars in thousands, except share amounts, unless otherwise noted.