Acquisitions	3 Months Ended
Mar. 31, 2014
Business Combinations [Abstract]
Acquisitions	2. ACQUISITIONS *Torus Insurance Holdings Limited* On April 1, 2014, Kenmare Holdings Ltd. (“Kenmare”), a wholly-owned subsidiary of the Company, together with Trident V, L.P., Trident V Parallel Fund, L.P. and Trident V Professionals Fund, L.P., which are managed by Stone Point Capital LLC (collectively, “Trident”), completed the previously announced acquisition of Torus Insurance Holdings Limited (“Torus”). Torus is an A- rated global specialty insurer with six wholly-owned insurance vehicles, including Lloyd’s Syndicate 1301. At closing, Torus became directly owned by Bayshore Holdings Ltd. (“Bayshore”), which was 60% owned by Kenmare and 40% owned by Trident. The purchase price for Torus was established in the amended and restated amalgamation agreement as $646.0 million, to be paid partly in cash and partly in the Company’s stock. The number of Company shares to be issued was fixed at the signing of the amalgamation agreement on July 8, 2013 and was determined by reference to an agreed-upon value per share of $132.448, which was the average closing price of the Company’s voting ordinary shares, par value $1.00 per share (the “Voting Ordinary Shares”), over the 20 trading days prior to such signing date. On the day before closing of the amalgamation, the Voting Ordinary Shares had a closing price of $136.31 per share. At closing, the Company contributed cash of $41.6 million towards the purchase price and $3.6 million towards related transaction expenses, as well as 1,898,326 Voting Ordinary Shares and 714,015 shares of Series B Convertible Participating Non-Voting Perpetual Preferred Stock of the Company (the “Non-Voting Preferred Shares”). Based on a price of $136.31 per share, the Company’s contribution of cash and shares to the purchase price totaled $397.7 million in the aggregate. Trident contributed cash of $258.4 million towards the purchase price and $2.4 million towards related transaction expenses. FR XI Offshore AIV, L.P., First Reserve Fund XII, L.P., FR XII A Parallel Vehicle L.P. and FR Torus Co-Investment, L.P. (collectively, “First Reserve”) received 1,501,211 Voting Ordinary Shares, 714,015 Non-Voting Preferred Shares and cash consideration in the transaction. Corsair Specialty Investors, L.P. (“Corsair”) received 397,115 Voting Ordinary Shares and cash consideration in the transaction. The remaining Torus shareholders received all cash. As a result of the amalgamation, First Reserve now owns approximately 9.5% and 11.5%, respectively, of the Company’s Voting Ordinary Shares and outstanding share capital. Upon the closing of the Torus acquisition, Bayshore, Kenmare and Trident entered into a Shareholders’ Agreement (the “Bayshore Shareholders’ Agreement”), which was subsequently amended, as described in “Dowling Co-investments in Bayshore and Northshore” below. *Changes in Ownership Interests relating to Holding Companies for our Active Underwriting Businesses* Atrium Employee Equity Awards On April 17, 2014, Northshore Holdings Ltd. (“Northshore”), the parent company of Atrium Underwriting Group Limited (“Atrium”) and Arden Reinsurance Company Ltd. (“Arden”), implemented long-term incentive plans that awarded time-based restricted shares of Northshore to certain Atrium employees. These equity awards will have the effect of modestly reducing Kenmare’s 60% equity interest in Northshore (as well as Trident’s 40% equity interest) over the course of the vesting periods as Atrium employees acquire shares. Shares generally vest over two to three years, and certain awards begin vesting in 2014. On a fully diluted basis, and assuming full vesting of all of these equity awards, the impact of the share awards are that Kenmare, Trident and certain Atrium employees own 57.1%, 38.1%, and 4.8% of Northshore, respectively. Dowling Co-investments in Bayshore and Northshore On May 8, 2014, Dowling Capital Partners I, L.P. (“Dowling”) purchased common shares of both Bayshore and Northshore from Kenmare and Trident (on a pro rata basis in accordance with their respective interests) for an aggregate amount of $15.4 million. Prior to the sale of shares to Dowling, Kenmare and Trident owned 60% and 40% of Bayshore, respectively, and 57.7% and 38.1% of Northshore on a fully diluted basis, respectively (assuming full vesting of Atrium employees’ restricted shares totaling 4.8%). Following the sale of Bayshore shares to Dowling, Kenmare, Trident and Dowling own 59%, 39.3% and 1.7% of Bayshore, respectively. Following the sale of Northshore shares to Dowling, Kenmare, Trident, certain Atrium employees and Dowling own 56.1%, 37.4%, 4.8% and 1.7% of Northshore, respectively, on a fully diluted basis. In connection with the sale of Bayshore shares, the Bayshore Shareholders’ Agreement was amended and restated. The Amended and Restated Bayshore Shareholders’ Agreement, among other things, provides that Kenmare has the right to appoint three members to the Bayshore board of directors and Trident has the right to appoint two members. The Amended and Restated Bayshore Shareholders’ Agreement includes a five-year period (the “Restricted Period”) during which no shareholder can transfer its ownership interest in Bayshore to a third party unless approved by a super-majority of the shareholders. Following the Restricted Period: (i) each shareholder must offer Kenmare and Trident the right to buy its shares before the shares are offered to a third party; (ii) Kenmare can require each other shareholder to participate in a sale of Bayshore to a third party as long as Kenmare owns 55% of the aggregate number of outstanding shares of Bayshore held by Kenmare and Trident; (iii) each shareholder has the right to be included on a pro rata basis in any sales made by another shareholder; and (iv) each of Kenmare, Trident and Dowling has the right to buy its pro rata share of any new securities issued by Bayshore. The Amended and Restated Bayshore Shareholders’ Agreement also provides that during the 90-day period following the fifth anniversary of the Torus closing, and at any time following the seventh anniversary of such closing, Kenmare would have the right to purchase the Bayshore shares owned by all other shareholders of Bayshore at their then fair market value, which would be payable in cash. Following the seventh anniversary of the Torus closing, Trident would have the right to require Kenmare to purchase all of Trident’s shares in Bayshore for their then current fair market value and Dowling would have the right to participate in such transaction by requiring Kenmare to purchase all of its shares in Bayshore on the same terms. Kenmare would have the option to pay for such shares either in cash or by delivering the Company’s Voting Ordinary Shares. In connection with the sale of Northshore shares, the Northshore Shareholders’ Agreement was amended and restated. The Amended and Restated Northshore Shareholders’ Agreement provides for substantially the same rights and obligations as the Amended and Restated Bayshore Shareholders’ Agreement, except that the fifth and seventh anniversaries refer to the Arden closing.

2. ACQUISITIONS

Torus Insurance Holdings Limited

On April 1, 2014, Kenmare Holdings Ltd. (“Kenmare”), a wholly-owned subsidiary of the Company, together with Trident V, L.P., Trident V Parallel Fund, L.P. and Trident V Professionals Fund, L.P., which are managed by Stone Point Capital LLC (collectively, “Trident”), completed the previously announced acquisition of Torus Insurance Holdings Limited (“Torus”). Torus is an A- rated global specialty insurer with six wholly-owned insurance vehicles, including Lloyd’s Syndicate 1301. At closing, Torus became directly owned by Bayshore Holdings Ltd. (“Bayshore”), which was 60% owned by Kenmare and 40% owned by Trident.

The purchase price for Torus was established in the amended and restated amalgamation agreement as $646.0 million, to be paid partly in cash and partly in the Company’s stock. The number of Company shares to be issued was fixed at the signing of the amalgamation agreement on July 8, 2013 and was determined by reference to an agreed-upon value per share of $132.448, which was the average closing price of the Company’s voting ordinary shares, par value $1.00 per share (the “Voting Ordinary Shares”), over the 20 trading days prior to such signing date. On the day before closing of the amalgamation, the Voting Ordinary Shares had a closing price of $136.31 per share. At closing, the Company contributed cash of $41.6 million towards the purchase price and $3.6 million towards related transaction expenses, as well as 1,898,326 Voting Ordinary Shares and 714,015 shares of Series B Convertible Participating Non-Voting Perpetual Preferred Stock of the Company (the “Non-Voting Preferred Shares”). Based on a price of $136.31 per share, the Company’s contribution of cash and shares to the purchase price totaled $397.7 million in the aggregate. Trident contributed cash of $258.4 million towards the purchase price and $2.4 million towards related transaction expenses. FR XI Offshore AIV, L.P., First Reserve Fund XII, L.P., FR XII A Parallel Vehicle L.P. and FR Torus Co-Investment, L.P. (collectively, “First Reserve”) received 1,501,211 Voting Ordinary Shares, 714,015 Non-Voting Preferred Shares and cash consideration in the transaction. Corsair Specialty Investors, L.P. (“Corsair”) received 397,115 Voting Ordinary Shares and cash consideration in the transaction. The remaining Torus shareholders received all cash. As a result of the amalgamation, First Reserve now owns approximately 9.5% and 11.5%, respectively, of the Company’s Voting Ordinary Shares and outstanding share capital.

Upon the closing of the Torus acquisition, Bayshore, Kenmare and Trident entered into a Shareholders’ Agreement (the “Bayshore Shareholders’ Agreement”), which was subsequently amended, as described in “Dowling Co-investments in Bayshore and Northshore” below.

Changes in Ownership Interests relating to Holding Companies for our Active Underwriting Businesses

Atrium Employee Equity Awards

On April 17, 2014, Northshore Holdings Ltd. (“Northshore”), the parent company of Atrium Underwriting Group Limited (“Atrium”) and Arden Reinsurance Company Ltd. (“Arden”), implemented long-term incentive plans that awarded time-based restricted shares of Northshore to certain Atrium employees. These equity awards will have the effect of modestly reducing Kenmare’s 60% equity interest in Northshore (as well as Trident’s 40% equity interest) over the course of the vesting periods as Atrium employees acquire shares. Shares generally vest over two to three years, and certain awards begin vesting in 2014. On a fully diluted basis, and assuming full vesting of all of these equity awards, the impact of the share awards are that Kenmare, Trident and certain Atrium employees own 57.1%, 38.1%, and 4.8% of Northshore, respectively.

Dowling Co-investments in Bayshore and Northshore

On May 8, 2014, Dowling Capital Partners I, L.P. (“Dowling”) purchased common shares of both Bayshore and Northshore from Kenmare and Trident (on a pro rata basis in accordance with their respective interests) for an aggregate amount of $15.4 million.

Prior to the sale of shares to Dowling, Kenmare and Trident owned 60% and 40% of Bayshore, respectively, and 57.7% and 38.1% of Northshore on a fully diluted basis, respectively (assuming full vesting of Atrium employees’ restricted shares totaling 4.8%). Following the sale of Bayshore shares to Dowling, Kenmare, Trident and Dowling own 59%, 39.3% and 1.7% of Bayshore, respectively. Following the sale of Northshore shares to Dowling, Kenmare, Trident, certain Atrium employees and Dowling own 56.1%, 37.4%, 4.8% and 1.7% of Northshore, respectively, on a fully diluted basis.

In connection with the sale of Bayshore shares, the Bayshore Shareholders’ Agreement was amended and restated. The Amended and Restated Bayshore Shareholders’ Agreement, among other things, provides that Kenmare has the right to appoint three members to the Bayshore board of directors and Trident has the right to appoint two members. The Amended and Restated Bayshore Shareholders’ Agreement includes a five-year period (the “Restricted Period”) during which no shareholder can transfer its ownership interest in Bayshore to a third party unless approved by a super-majority of the shareholders. Following the Restricted Period: (i) each shareholder must offer Kenmare and Trident the right to buy its shares before the shares are offered to a third party; (ii) Kenmare can require each other shareholder to participate in a sale of Bayshore to a third party as long as Kenmare owns 55% of the aggregate number of outstanding shares of Bayshore held by Kenmare and Trident; (iii) each shareholder has the right to be included on a pro rata basis in any sales made by another shareholder; and (iv) each of Kenmare, Trident and Dowling has the right to buy its pro rata share of any new securities issued by Bayshore.

The Amended and Restated Bayshore Shareholders’ Agreement also provides that during the 90-day period following the fifth anniversary of the Torus closing, and at any time following the seventh anniversary of such closing, Kenmare would have the right to purchase the Bayshore shares owned by all other shareholders of Bayshore at their then fair market value, which would be payable in cash. Following the seventh anniversary of the Torus closing, Trident would have the right to require Kenmare to purchase all of Trident’s shares in Bayshore for their then current fair market value and Dowling would have the right to participate in such transaction by requiring Kenmare to purchase all of its shares in Bayshore on the same terms. Kenmare would have the option to pay for such shares either in cash or by delivering the Company’s Voting Ordinary Shares.

In connection with the sale of Northshore shares, the Northshore Shareholders’ Agreement was amended and restated. The Amended and Restated Northshore Shareholders’ Agreement provides for substantially the same rights and obligations as the Amended and Restated Bayshore Shareholders’ Agreement, except that the fifth and seventh anniversaries refer to the Arden closing.