Berkshire Hathaway is a holding company with a wide array of subsidiaries engaged in diverse activities. The firm's core business segment is insurance, run primarily through Geico, Berkshire Hathaway Reinsurance Group and Berkshire Hathaway Primary Group. Berkshire has used the excess cash thrown off from these and its other operations over the years to acquire Burlington Northern Santa Fe (railroad), Berkshire Hathaway Energy (utilities and energy distributors), and the firms that make up its manufacturing, service, and retailing operations (which include five of Berkshire's largest noninsurance pretax earnings generators: Precision Castparts, Lubrizol, Clayton Homes, Marmon and IMC/ISCAR). The conglomerate is unique in that it is run on a completely decentralized basis.

Berkshire Hathaway is a holding company with a wide array of subsidiaries engaged in diverse activities. The firm's core business segment is insurance, run primarily through Geico, Berkshire Hathaway Reinsurance Group and Berkshire Hathaway Primary Group. Berkshire has used the excess cash thrown off from these and its other operations over the years to acquire Burlington Northern Santa Fe (railroad), Berkshire Hathaway Energy (utilities and energy distributors), and the firms that make up its manufacturing, service, and retailing operations (which include five of Berkshire's largest noninsurance pretax earnings generators: Precision Castparts, Lubrizol, Clayton Homes, Marmon and IMC/ISCAR). The conglomerate is unique in that it is run on a completely decentralized basis.

ACE acquired Chubb in the first quarter of 2016 and assumed the Chubb name. The combination makes the new Chubb one of the largest domestic property and casualty insurers, with operations in 54 countries spanning commercial and personal P&C insurance, reinsurance, and life insurance.

Headquartered in Beijing and commanding around 20% share, China Life Insurance is a dominant player in the Chinese life insurance industry. The firm offers group and individual life insurance through exclusive agents, bancassurance, and other marketing platforms. While the bulk of profits stem from life insurance policies, additional operations include short-term policies such as accident and health insurance. The company is currently undergoing a business transformation toward the sale of long-term protection products and away from short-term and single-premium products.

Marsh & McLennan is a professional-services firm that provides advice and solutions in the areas of risk, strategy, and human capital. The company operates through two main segments: risk and insurance services and consulting. In risk and insurance services, the firm offers services via Marsh (an insurance broker) and Guy Carpenter (a risk and reinsurance specialist). The consulting division comprises Mercer (a provider of human resource services) and Oliver Wyman (a management and economic consultancy).

American International Group is one of the largest insurance and financial services firms in the world and has a global footprint. It operates through a wide range of subsidiaries that provide property, casualty, and life insurance. Its revenue is split roughly evenly between commercial and consumer lines.

MetLife--once a mutual company before the 2000 demutualization--is the largest life insurer in the U.S. by assets and provides a variety of insurance and financial services products. Outside the United States, MetLife operates in Japan and more than 50 countries in Latin America, the Asia-Pacific region, Europe, and the Middle East.

Progressive underwrites private and commercial auto insurance and specialty lines; it has roughly 20 million policies in force and is the fourth- largest auto insurer in the United States. Progressive markets its policies through independent insurance agencies in the U.S. and Canada and directly via the Internet and telephone. Its premiums are split roughly equally between the agent and the direct channel. The company entered homeowners insurance through an acquisition in 2015.

Aon is a leading global provider of insurance and reinsurance brokerage and human resource solutions. Its operations are tilted toward its brokerage operations. Headquartered in London, Aon has about 50,000 employees and operations in 120 countries around the world.