When it comes to bank stocks, size does indeed matter.

Not only do the largest regional banks -- including SunTrust Banks (NYSE:STI), BB&T (NYSE:TFC), and Capital One (NYSE:COF) -- benefit from economies of scale, but they're also typically much more diversified than their community banking counterparts. These are two of the reasons that shares of Capital One and BB&T, after adjusting for dividends and buybacks, have outperformed the S&P 500 over the past two decades.

Given this, investors in bank stocks should keep a rough tally of where specific banks fall in the size spectrum. The slideshow below does just that, using data from the third-quarter earnings releases of SunTrust Banks, BB&T, Capital One, and others, to rank the biggest regional banks in the United States by total assets.