What happened

Shares of Citigroup (C -1.02%) were trading more than 5% higher in pre-market trading at 9:19 a.m. ET today after the large bank reported second-quarter earnings results that smashed analyst estimates.

So what

Citigroup reported diluted earnings per share of $2.19 on total revenue of roughly $19.6 billion. The Street had been projecting earnings per share of only $1.68 and revenue of $18.2 billion.

Citigroup's largest revenue generator, its Institutional Clients Group, reported revenue of more than $11.4 billion, up 2% from the previous quarter and 20% year over year. Within the unit, the bank's Treasury and Trade Solutions (TTS) group had a superb quarter, generating more than $3 billion of revenue, up 17% from the prior quarter and 33% year over year.

CEO Jane Fraser often refers to TTS as the "crown jewel" of the bank and said the unit "fired on all cylinders as clients took advantage of our global network, leading to the best quarter this business has had in a decade."

Citigroup also saw nice growth in branded credit cards, with balances up 4% from the prior quarter and 10% year over year.

The bank also reported a net release of credit reserves in its Institutional Clients Group, largely driven by reducing its exposure in Russia, something investors have been worried about in recent months.

Now what

After disappointing earnings from JPMorgan Chase and Morgan Stanley yesterday, I didn't know what to expect coming into today, but I thought this was a great print for Citigroup, especially considering the way it highlighted the power of the TTS business.

The bank is in the midst of a turnaround, and while there is still a lot of work to do, this was a nice quarter, and I remain bullish on the stock.