Stocks are generally lower today as we continue our progress into earnings season with Wells Fargo (NYSE:WFC) coming up short of expectations this morning. At roughly halfway through the trading session, the Dow Jones Industrial Average (DJINDICES:^DJI) is down by a negligible 6 points, or 0.04%.

While the fourth-quarter results from Wells Fargo have sparked a sell-off in financial stocks, don't let that fool you. The nation's fourth-largest bank by assets is essentially minting money at this point. For the final quarter of 2012, the lender reported earnings of $5.1 billion, or $0.91 per share, compared to $4.1 billion, or $0.73 per share, from the prior-year period -- for those of you counting, that equates to an annual growth rate of 24%. For the full year, meanwhile, the bank earned $18.9 billion, a 20% increase over 2011. Both figures were records for the company.

Stating the obvious, Wells Fargo's CEO, John Stumpf, noted: "2012 was an outstanding year for Wells Fargo. We saw the continued benefits of our diversified business model and reported record full year and fourth quarter earnings, robust deposit and solid loan growth, and strong performance across our business units."

The only downside, and the reason financial stocks like Bank of America (NYSE:BAC) and JPMorgan Chase (NYSE:JPM) have fallen on the news, is that the mortgage giant's net interest margin, or NIM, fell to 3.56%, down from 3.66% in the third quarter of 2012 and 3.89% in the fourth quarter of 2011. As I discussed in my earnings preview of Wells Fargo, this is one of the most important metrics in the banking industry. It measures the difference between a lender's yield on earning assets (primarily loans) and its cost of funds (primarily deposits). Any fall in this figure, in turn, suggests that leaner times might be ahead for the industry -- although, given Wells Fargo's earnings the last few quarters, I don't think investors should be overly concerned.

Next week sees a large number of financial companies reporting earnings. JPMorgan, Goldman Sachs, and US Bancorp report on Wednesday; Bank of America, Citigroup, and BB&T release on Thursday; and SunTrust Banks wraps up the week on Friday. Check back here for comprehensive earnings coverage on all of those companies.

John Maxfield owns shares of Bank of America. The Motley Fool recommends Goldman Sachs Group and Wells Fargo & Company. The Motley Fool owns shares of Bank of America, Citigroup Inc , JPMorgan Chase & Co., and Wells Fargo & Company. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.