When investors think of big banks such as Wells Fargo (NYSE:WFC) and JPMorgan Chase (NYSE:JPM), most think of mortgages. After all, these two behemoths are first and second in the mortgage business.

But a much smaller business -- credit cards -- is performing incredibly well for at least one major bank, which bodes well for the industry as a whole.

JPMorgan's card business is on a tear
JPMorgan is the largest card issuer and credit card company in the world, reporting average credit card balances of $127.8 billion in its most recent earnings supplement. As credit card balances grow, the rate at which customers repay their debts is improving. JPMorgan's charge-off rate fell to 2.85%, down from 3.5% just one year ago.

And it looks as if the trend will only continue. This quarter, only 1.67% of balances were in the 30-day-plus delinquency column, down from 2.1% in the year-ago period.

Wells Fargo's quarter showed similar year-over-year improvement. The company reported that net charge-offs tallied to 3.38% of average loans, down from 3.7% one year ago.

Why JPMorgan trumps Wells Fargo in cards
Compared with most credit card companies, including Wells Fargo, JPMorgan's Chase brand counts the most creditworthy borrowers as cardholders. It's safe to put it up there with American Express (NYSE:AXP), another "prime" credit card issuer.

A quick look at comparison site CreditKarma shows their average member approved for a Chase Sapphire card had a credit score of 745, compared with a 726 score for American Express' Everyday card. Wells Fargo's ordinary Visa credit cardholder had an average score of 696.

What's interesting here is whether Wells Fargo's and JPMorgan's results will be a a bellwether for the credit card industry as a whole.

Capital One and American Express report earnings on Jan. 16. Discover Financial Services follows on January 23. Last year, the industry reported that charge-offs hit a level not seen since 1990. If the trend of low delinquencies continues, credit card companies could be set to log a very impressive 2014.