As used in this report, references to "we," "us," "our," "Arch" or the "Company" refer to the consolidated operations of Arch Capital Group Ltd. ("Arch Capital") and its subsidiaries. Tabular amounts are in U.S. Dollars in thousands, except share amounts, unless otherwise noted. We refer you to Item 1A "Risk Factors" for a discussion of risk factors relating to our business.
Arch Capital, a Bermuda public limited liability company with $11.17 billion in capital at December 31, 2018, provides insurance, reinsurance and mortgage insurance on a worldwide basis through its wholly owned subsidiaries. While we are positioned to provide a full range of property, casualty and mortgage insurance and reinsurance lines, we focus on writing specialty lines of insurance and reinsurance. For 2018, we wrote $5.35 billion of net premiums and reported net income available to Arch common shareholders of $713.6 million. Book value per share was $21.52 at December 31, 2018, compared to $20.30 per share at December 31, 2017.
Arch Capital was formed in September 2000 and became the sole shareholder of Arch Capital Group (U.S.) Inc. ("Arch-U.S.") pursuant to an internal reorganization transaction completed in November 2000. In October 2001, Arch Capital launched an underwriting initiative to meet current and future demand in the global insurance and reinsurance markets that included the recruitment of new management teams and an equity capital infusion of $763.2 million. Since that time, we