Why don't insurance companies give more donations to politicians?

Here is the top 100 donors to Congress. You see the AMA, dentists, pharmaceutical companies. You see everyone that's going to make out like a bandit when reform passes. I see a single insurance company represented. If the big evil health insurance companies are so rich, why haven't they been the biggest donors?

House Speaker Nancy Pelosi ridiculed criticism by Republican Senate Leader Mitch McConnell of Democrats’ health-care plans, saying he’s echoing an insurance industry which makes “exorbitant profits” at the expense of Americans’ well being.

Why aren't they turning those exorbitant profits into massive donations like the other businesses do? The industry that's made the smallest donations is being singled out as the root of all health care woes.