TD Ameritrade (AMTD - Get Report) , the online brokerage firm, said CEO Tim Hockey would depart in February, and that the company would engage national search firms to help recruit his successor, including both internal and external candidates.

Joe Moglia, chairman of the board and a former TD Ameritrade CEO, said in a press release after the market close on Monday that the successor will guide the "next phase of growth." Shares of TD Ameritrade were down 0.86% to $51.95 in after-hours trading.

Hockey will move into an advisory role if a new CEO is hired before February, according to the Omaha, Nebraska-based company.

"We are grateful to Tim for his leadership and the contributions he made," Moglia said.

Hockey, 56, said in an interview after the surprise announcement that he wasn't leaving for another job, and that he was healthy. He and his management team have been successfully carrying out a strategy set by the board of directors, he said.

He declined to detail any specific points of disagreement with the board. 

"By definition these conversations are nuanced and have to remain behind closed doors," he said. "One party says to the other, We should talk. And then you have those conversations. And at the end of them, we agreed it was time to part ways." 

TD Ameritrade's gain of roughly 7% this year trails the the Standard & Poor's 500 Index's 19% increase on the year, but it's almost double the 3.9% gain at rival Charles Schwab (SCHW - Get Report) .

Indeed, the pending leadership change came as TD Ameritrade said profit rose 23% during its most-recent fiscal quarter, beating analysts' expectations.

Net income during the fiscal third quarter ending on June 30 was $555 million, up from $451 million a year earlier, the company said.

Adjusted earnings per share were $1.04, exceeding the 97-cent average estimate of analysts in a survey by data provider FactSet.

TD Ameritrade's clients averaged 824,600 trades per day during the period, up from 783,665 a year earlier but down from 860,359 during the three months through March.

And customers added $19.5 billion to their accounts, bringing total client assets to $1.31 trillion.

Revenue rose by 8% from a year earlier to $1.49 billion, while operating expenses rose by just 2.7% to $771 million.

In the interview, Hockey said that although U.S. stocks have recently charted new record highs, many investors are skittish about pumping more of their wealth into the market.

Factors range from uncertainty over how long the current decade-old economic expansion can last, to questions over future Federal Reserve interest rates, to the murky outlook for a resolution to President Donald Trump's trade war with China, he said. 

"That makes people wonder if we're at the frothy top," he said. "On the other hand, the market continues to prove all the pundits wrong."

Despite the lackluster trading environment, TD Ameritrade gained market share from rivals during the second quarter, Hockey said.