After being down 0.17% in overnight trading, Citigroup (C -1.11%) is up 1.58% about two and half hours into the trading day. All four of the big banks are up, along with all three major indices, but Citi may have more going for it than just herd dynamics.

Market roundup
But before get into that, here's a quick look at where Citi's peers and the markets are shaking out so far:

  • Bank of America is up a healthy 1.36%.
  • Wells Fargo is up a solid 1.18%.
  • And JPMorgan Chase is leading the pack: up by 1.55%.

The markets are all in the green, as well, with the broader S&P 500 up by 0.27%, the narrower Dow Jones Industrial Average up 0.09%, and the Nasdaq Composite up 0.35%.

Bank vs. bank
The Wall Street Journal is reporting that Citi has filed suit against British banking-giant Barclays (BCS 7.29%) for $141 million, over losses Citi allegedly incurred by providing Lehman Brothers with currency-clearing services in the week between the imploding investment bank's bankruptcy filing and its liquidation.

Citi claims it had no exposure to Lehman at that time, but provided the currency-clearing service to Barclays because the British superbank was trying to buy Lehman's North American businesses in that desperate week. Per the complaint, Citi had tried to recover its money directly from Barclays, but Barclays refused to pay. 

Foolish bottom line
For the country's third-largest bank, $141 million isn't much, but when you're trying to repair a balance sheet still significantly affected by the financial crisis, every little bit helps. As such, investors might be rewarding Citi for its assertiveness in going after what it rightly feels belongs to it.

I'm a Citi investor, and I know I was happy to see this news. I feel Citi is in a crucial moment of turnaround, with CEO Michael Corbat quietly but firmly taking charge of the superbank and looking out for its long-term interests. Stories like this only bolster that happy feeling.

Of course, it could also be that this lawsuit news is having no appreciable impact on today's share-price performance. It is a happy day in the markets, with all the big four banks up along with the three major indices. Citi may just be going along for the ride.

And that's the kind of thing you always have to consider when you're an investor. There's rarely a clear-cut reason for a stock's performance. And even if there is, it's important to focus on the long term rather than the short term. The markets can spike and plummet on a day-to-day, week-to-week, or even month-to-month basis, which is why you should only be checking in on your stock at most once a month, or even once a quarter. So long as the companies you're invested in have solid fundamentals, have faith that your money is in the right place. Long-term thinking is what investing Foolishly is all about.