Here are several helpful breakdowns by Investopedia by Insurance industry category.
Non-health Insurance Companies
| Company Name | Market Capitalization |
| Berkshire Hathaway (BRK.A) | $308 billion |
| China Life Insurance (LFC) | $80 billion |
| Allianz (AZSEY) | $76.8 billion |
| American International Group (AIG) | $72.3 billion |
| Ping An of China (PNGAY) | $65.6 billion |
| MetLife (MET) | $59.4 billion |
| AXA (AXA) | $57.8 billion |
| AIA Group Hong Kong (AAIGF) | $54.4 billion |
| ING Groep (ING) | $54.4 billion |
| Zurich Insurance (ZURVY) | $45.4 Billion |
(Source: Thompson Reuters)
Health Insurance and Managed Health Care Companies
| Company Name | Market Capitalization |
| United Healthcare (UNH) | $91.8 billion |
| Wellpoint (WLP) | $34.3 billion |
| Aetna (AET) | $29.8 billion |
| CIGNA Corp. (CI) | $26.8 billion |
| Humana (HUM) | $21.1 billion |
| Centene Corp. (CNC) | $5.7 billion |
| Health Net, Inc. (HNT) | $3.9 billion |
| WellCare Health Plans (WCG) | $3.1 billion |
| Healthspring (HS) | $3.7 billion |
| Molina Healthcare (MOH) | $2.4 billion |
(Source: Thompson Reuters)
Property & Casualty
| Company | Net Premiums Written |
| State Farm Group | $50.8 billion |
| Allstate Insurance Group (ALL) | $24.8 billion |
| Liberty Mutual | $21.5 billion |
| Berkshire Hathaway (includes GEICO) | $21.4 billion |
| Travelers Group (TRV) | $20.6 billion |
| American International Group (AIG) | $19.7 billion |
| Nationwide Group | $14.5 billion |
| Progressive Insurance Group (PGR) | $14.5 billion |
| Farmers Insurance Group | $14.1 billion |
| USAA Group | $10.7 billion |
(Source A.M. Best)
Life Insurance Companies
| Company | Total Direct Premium | Market Share |
| MetLife (MET) | $11.5 billion | 7.98% |
| Northwestern Mutual | $9.4 billion | 6.55% |
| Prudential of America (PRU) | $8.4 billion | 5.79% |
| New York Life | $7.8 billion | 5.42% |
| Lincoln National | $6.1 billion | 4.27% |
| MassMutual | $5.1 billion | 3.52% |
| John Hancock | $4.8 billion | 3.37% |
| Aegon (AEG) | $4.1 billion | 2.82% |
| State Farm | $4.0 billion | 2.79% |
| Guardian Life Insurance Co. | $3.4 billion | 2.34% |
(Source: NAIC)
Health Insurance Companies
| Company | Total Direct Premium | Market Share |
| United Healthcare (UNH) | $66.8 billion | 11.70% |
| Wellpoint Group (WLP) | $55.7 billion | 9.75% |
| Kaiser Permanente | $43.7 billion | 7.66% |
| Humana (HUM) | $21.7 billion | 3.81% |
| Aetna (AET) | $21.7 billion | 3.81% |
| Health Care Service Corp | $14.9 billion | 2.60% |
| American Family | $11.6 billion | 2.04% |
| Highmark | $11.4 billion | 2.01% |
| Blue Cross/Blue Shield | $9.8 billion | 1.72% |
| Cigna (CI) | $9.6 billion | 1.69% |
(Source: NAIC. Caveat emptor: The sales data on health insurance companies is from 2007, the last year of available data. The Affordable Care Act (aka ‘Obamacare’) may have altered these standings.)