Editor's note: What follows are the top 10 donors to liberal outside groups, then the top 10 donors to conservative outside groups.

The final numbers are not yet in, but the 2014 elections were on track to be the most expensive midterms in history.

The Center for Responsive Politics estimated the midterms would cost $3.67 billion -- slightly more than $3.63 billion in 2010 and nearly as much as the $4 billion spent in the last presidential race.

But it wasn't just candidates and parties spending the cash. After the 2010 Supreme Court ruling on Citizens United, the floodgates opened, allowing outside groups to spend record amounts.

Four years ago, outside spending came to more than $300 million. This year that figure is expected to triple, according to the CRP.

This includes money spent by groups such as super PACs, which are legally allowed to raise and spend unlimited amounts as long as they don't donate directly to candidates or coordinate with their campaigns. Some argue this money creates "shadow campaigns" that can dominate the election dialogue.

So who gives to these outside groups? Corporations, unions and associations can all contribute, as can individuals.

Using data gathered by the CRP, CNN looked at the top individual donors giving to liberal and conservative outside groups.

Not all of these outside groups are required to disclose their sources of income -- which explains why people like the Koch brothers and Karl Rove aren't listed here.

Those who are, however, have a good bit in common: Many are hedge fund managers and real estate investors who went to Harvard, contribute significantly to charities and sit on nonprofit boards. Most are self-made billionaires.

But they also have unusual stories:

One sold bedpans before he made it big, another managed vending machines, and one put himself through school working as a waiter and a parking lot attendant.

Another pretended to be a Christian boy named Sandor Kiss to escape the fate of millions of his countrymen murdered by the Nazis.

Two worked as code breakers to help the government. Several have interesting outside “hobbies,” having owned race horses or professional sports teams.

One has jammed with the rocker Meatloaf on stage.

Take a look behind the numbers and learn more about these big donors and how they made their money.

First are the top 10 donors to liberal outside groups, followed by the top 10 donors to conservative outside groups.