Earlier this month, Bank of America (NYSE:BAC) sent shock waves through the credit card industry when it unveiled plans to acquire MBNA (NYSE:KRB), the world's largest independent provider of plastic. Still, the news wasn't a total surprise, because two high-profile marriages between banks and credit card issuers paved the way for this union. A month before, Washington Mutual (NYSE:WM) announced a similar arrangement, after it concluded that buying Providian's (NYSE:PVN) already-established business would be more cost-effective than developing its own line of cards.

It was Capital One (NYSE:COF) that got the ball rolling when it became enamored with a Southern belle named Hibernia (NYSE:HIB) in March. Not only could Hibernia, a fast-growing regional bank, provide a retail platform to augment the card giant's ubiquitous direct marketing efforts, but also Capital One could tap the rather attractive $17 billion deposit base as a cheap source of funds to support its lending operations.

With this merger expected to be completed in a few weeks, Capital One is flexing its financial muscles. Yesterday, the company reported second-quarter earnings of $2.03, a sharp 23% improvement from the $1.65 earned a year ago, and a dime ahead of analysts' expectations. Revenues climbed 16.5% to $2.45 billion, with net interest income rising 22.7% and non-interest fee income rising 13.3%.

Along with steadily growing earnings, Capital One has consistently increased its loan portfolio every year since the company's IPO in 1994. This year looks to be no exception, as managed loans are up by $9.6 billion, or 13%, from this point last year, and now stand at more than $83 billion. Management is forecasting continued double-digit growth in this category for the rest of the year, with the auto finance and global financial services divisions leading the way.

As the mature credit card market continues to slow, Capital One's diversification is beginning to pay off. Last year, while the company's new and existing cardholders ran up their collective balance by only 5%, the auto and global finance segments registered loan growth of 18% and 28%, respectively. This trend continued last quarter as net income generated by the auto finance division soared 170% on solid loan growth and both earnings and receivables from credit cards trailed off slightly from the first quarter.

However, with MBNA set to move under the Bank of America umbrella, there may soon be a void in the agent banking marketplace -- where financial institutions without a card of their own team up with card issuers to provide one for their customers. But banks like Wachovia (NYSE:WB) that are partners with MBNA might not want a major competitor to fill their customers' needs, and some may be reluctant to continue the relationship. As one of the few remaining independent card issuers, Capital One will be well-positioned to capture much of this business.

Investors looking for stock in a card company could do worse than Capital One, but don't forget to examine the fine print first.

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Fool contributor Nathan Slaughter carries no Capital One cards, but he does own shares of Bank of America.