(AP Photo/Matt Rourke, File)

10. Cigna (No. 103 overall)

$29.1 billion in revenue ($1.623 billion in profit)

Cigna kicks off the list at a good time. The diversified carrier's stock just hit a 52-week high, and analyst expecations are high for its second quarter earnings call Aug. 1.

9. TIAA-CERF (No. 97 overall)

$32.2 billion in revenue ($2.060 billion in profit)

Life insurer – and nonprofit specialist – TIAA-CREF is probably better-known in retirement circles than in benefit broker gatherings, but when you make this list, and another mainstream magazine's top mutual fund list, you've earned inclusion.

8. Massachusetts Mutual Life Insurance (No. 94 overall)

$32.9 billion in revenue ($1.114 billion in profit)

While MassMutual's presence in the news lately has been more focused on its acquisition strategy, and its subsequent growth in the TPA space, the carrier's quietly been making a huge diversity push, targeting growth markets its competitors might be missing.

7. New York Life Insurance (No. 89 overall)

$34.3 billion in revenue ($1.333 billion in profit)

New York Life is the undisputed top dog in the fixed immediate annuity market, but its life insurance presence is worth noting, as well, especially after its agents booked a 20 percent jump in life insurance sales last quarter.

(AP Photo/Wilfredo Lee)

6. Aetna (No. 84 overall)

$36.6 billion in revenue ($1.657 billion in profit)

Aetna made news not too long ago by pulling out of the individual market in California. But this major medical carrier is one of three on this list pushing hard in the accountable care organization space, along with Cigna and UnitedHealth. But what did make headlines was its announced 5 percent rate cut on the D.C. public exchange.

(AP Photo/Ed Reinke)

5. Humana (No. 73 overall)

$39.1 billion in revenue ($1.222 billion in profit)

The execs at Humana are no strangers to government medical plans despite the fact their CEO, Bruce Broussard, took the helm as recently as January. They've been in the Medicare Advantage business for years. They also plan to compete in the exchanges in at least 14 states.

(AP Photo/Michael Conroy)

4. Wellpoint (No. 47 overall)

$61.7 billion in revenue ($2.655 billion in profit)

The news has been decidedly mixed at health care giant Wellpoint over the last few months: Its California subsidiary's rate hikes for the exchanges drew sticker shock in May. In early June its stock hit a 52-week high. Then it settled a suit with Los Angles over "improperly dropped policyholders" for $6 million (maybe it's California?).

(AP Photo/Mark Lennihan)

3. MetLife (No. 40 overall)

$68.2 billion in revenue ($1.324 billion in profit)

Analysts are bullish on Metlife – fully recovered from the economic collapse that sent so many Fortune 500 companies reeling. The insurer is consolidating  its subsidiaries to cut costs while eyeing a larger presence in a growing Asian market.

(AP Photo/Douglas C. Pizac, file)

2. Prudential Financial (No. 29 overall)

$84.8 billion in revenue ($469 million in profit)

Prudential Financial isn't just the second largest player in the life insurance – trailing only MetLife – it's No. 2 on this list as well. And things are only looking up, with the stock surging this year, its advance in the Japanese market and their takeover of a couple of pretty big automaker pensions.

(AP Photo/Jim Mone)

1. UnitedHealth Group (No. 17 overall)

$110.6 billion in revenue ($5.526 billion in profit)

And last, and far from least, is the 800-pound gorilla in the (emergency) room: UnitedHealth Group, who's more than $110 billion in revenue propelled it into the top 20 overall. And despite being the second carrier in a month to pull out of California's individual market, the experts over at Barron's expect the company's stock to balloon more than 40 percent over the next two years. This after a 22 percent jump this year alone. Its earning report next week should be interesting.