Arch Capital Group is a holding company. Through its subsidiaries, Co. provides insurance, reinsurance and mortgage insurance. Co.'s underwriting segments are: insurance, which includes construction and national accounts, excess and surplus casualty, lenders products, professional lines, programs, and property, energy, marine and aviation; reinsurance, which includes casualty, marine and aviation, other specialty, property catastrophe, and property excluding property catastrophe; and mortgage, which includes its U.S. primary mortgage insurance, U.S. credit risk transfer that are mainly with government sponsored enterprises and international mortgage insurance and reinsurance operations.