Huntington Bancshares (NASDAQ:HBAN) has a number of things going for it when it comes to reasons why someone should consider an investment in it -- but there is one key thing to know about this regional outfit that may escape the casual observer.

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Principally, Huntington operates in five states, Ohio, Michigan, Pennsylvania, Indiana, and West Virginia. But the competition in those states is stiff, as it not only has to deal with other Ohio-based regional bank Fifth Third Bancorp (NASDAQ:FITB), but also Pittsburg super-regional bank PNC (NYSE:PNC), and national megabanks Wells Fargo (NYSE:WFC) and JPMorgan Chase (NYSE:JPM).

But to Huntington's credit, it has actually been able to steadily grow its market share despite the strong competition it faces from other banks that have exponentially more resources -- as it even swapped places with Wells Fargo when checking market share dating back to 2010:

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Source: FDIC.

In fact, Wells Fargo watched its deposits actually fall by roughly $3.5 billion in those five states. All others watched theirs grow substantially, and while JPMorgan Chase was the clear winner in deposit growth, the 19.4% growth posted by Huntington was only narrowly bested by Fifth Third:

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Source: FDIC.

Of course, while deposit growth is a good thing, it's certainly not the only thing when it comes to a bank. And what investors are missing when it comes to Huntington isn't that it's gaining market share, but that it's actually doing so in an incredibly profitable way that will likely yield big results further down the road.

Growth in profitable relationships
In 2010 Huntington set out to grow both the "market share and share of the wallet" of its customers, through "best in class consumer products, customer service with increased marketing and branding, deep community involvement," and other various initiatives. Usually, companies can outline a whole host of things they say they will do and never come through on those, but that cannot be said of Huntington -- and investors need to know the data proves it.

Consider that in 2013, J.D. Power and Associates gave Huntington the highest customer satisfaction rating in the North Central region, which encompasses Indiana, Kentucky, Michigan, Ohio, and West Virginia, or every state where Huntington has a significant presence except for Pennsylvania. Its rating of 814 was certainly better than the 788 posted by JPMorgan Chase (the next closest of the five banks mentioned above), and well above the 776 average.

It isn't just that Huntington is delivering great customer service to its customers, but the following charts from a recent presentation to investors show that it is leveraging its customer service and the relationships it is building to bring more customers into more inclusive (and more profitable) relationships with it:

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Source: Company Investor Presentations.

Huntington also noted that its households with more than six services from the bank has grown from a little more than 41% of customers in 2011 to 47% of customers in the most recent quarter. This hasn't only happened in its consumer operations, but in its commercial arm, too; relationships there have grown by 28% since the middle of 2010, and commercial clients with more than four services from Huntington has grown from 22% to 37%.

The Foolish bottom line
All of this means that as Huntington continues to build entrenched relationships, it will be able to bolster the profits and income from each customer it's able to generate, which should translate straight to its bottom line, and to investors.

Fool contributor Patrick Morris has no position in any stocks mentioned. The Motley Fool recommends Wells Fargo. The Motley Fool owns shares of Fifth Third Bancorp, Huntington Bancshares, JPMorgan Chase, PNC Financial Services, and Wells Fargo. 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.