UnitedHealthcare is the insurance division of UnitedHealth Group Inc., which also operates the fast-growing health services business Optum.
Headquarters: Minnetonka.
2011 Revenue: $95.3 billion.
Number of people enrolled in plans: 35.6 million.
Who is covered: More than 26 million individuals, and workers at small businesses and large national employers; more than 3.3 million workers in municipalities, educational institutions and labor unions; 2.2 million people on Medicare and 3.5 million on Medicaid.
Sources: SEC filings, 2011 UnitedHealth Group report
