Larry Ellison just increased his personal credit line to nearly $10 billion, according to documents filed with the SEC, as spotted by Bloomberg's Caleb Melby and Laura Marcinek.

That's like having a $10 billion credit card. With a "b."

Ellison pledged 250 million shares of Oracle's stock as collateral for his personal line of credit. Shares are trading at about $39 a share as of Friday, making that credit line worth about $9.7 billion. That compares to 215 million shares he pledged last year and 139 million in 2012, reports Bloomberg. Oracle's share price has grown since 2012, so he's not just trying to maintain a credit limit, he's increasing it.

And why not? As the fifth-richest man in the world, his own net worth has risen since 2012, too, from about $37 billion to more than $48 billion.

Ellison is not shy about spending his money. He collects mansions, yachts, aircraft, race cars, art. He bought most of the Hawaiian island of Lanai for a reported $300 million, and not just one, but two airlines to serve it. He could spend up to $100 million this year on his America's Cup sailing team alone.

The credit line represents only a fraction of his Oracle stake, too. He owns 1.16 billion shares of Oracle, about 26% of the company, according to forms filed to the SEC. The shares pledged as collateral are less than 20% of that.

So between Oracle, his vast real estate holdings, and his other business interests (NetSuite, for example), the banks know he's good for the $10 billion, even if they want collateral.

A bigger question is why borrow money when you're swimming in it? There are a couple of possibilities. First, interest rates are low and Oracle's stock has been on the rise. It could be cheaper for him to borrow money than to sell stock and lose out on that growth.

If he wants to buy something that costs a lot, a loan could be a faster way to get his hands on the money. As a major officer at Oracle, he has to be careful about how quickly he sells a lot of stock. He can't flood the market with shares.

Plus, most execs need to avoid accusations of insider trading. He learned that the hard way. In 2005, Ellison paid $100 million to charity to settle an insider trading lawsuit, Infoworld reported at the time. Today most execs schedule their trades in advance to avoid any perception of insider trading.

Third, he actually prefers to hold onto his Oracle stock. Although he's granted millions of shares every year in stock options, he rarely sells them, according to insider trading forms filed with the SEC.

So there's a lot of reasons for Ellison to keep a humongous credit line available.

But sometimes we still have to stop and marvel at how much money the world's richest people could spend in an instant, on a whim.