Cooper was TCF's Chairman and CEO for 20 years. He left the CEO job in 2005, but he had planned to stay on as chairman through this year.
The announcement of Cooper's return as CEO follows a bad three months for the bank. Last week TCF reported its second-quarter profit fell 62 percent, as the number of bad loans it wrote off nearly quadrupled. And TCF announced a fivefold increase in its reserves to cover potential loan losses.
But lots of banks have been struggling and having down quarters, as the housing, auto and other sectors of the economy sputter, and those banks are not replacing their CEOs.
Cooper says he's returning, because Nagorske is tired of the banking business.
"He basically expressed to me that he was just burned out and, looking at the rest of his career, didn't want to be fighting these battles through a longer period," said Cooper.
But Cooper praised Nagorske's leadership and said Nagorske leaves with the bank's worst problems behind it.
"My personal opinion is that he picked this time, because I think he felt he had worked us into a situation where we had crested in terms of these problems and that it was an opportune time to do it," said Cooper.
Nagorske was not available for an interview.
The management change took a lot of folks in the investment community by surprise.
Mark Henneman is a portfolio manager at Mairs and Powers, a St. Paul investment firm with a sizable stake in TCF. He says they did not consider TCF to an institution in need of new leadership.
"There are a lot of banks in need of new leadership. And we didn't consider TCF to be one of them," said Henneman.
Henneman says TCF would be fine with either Nagorske or Cooper at the top.
"We've been pretty comfortable with Lynn Nagorske. And recently have been buying shares. But we're also very comfortable with Bill Cooper's management style," said Henneman.
Cooper insists the leadership change doesn't signal any big troubles or widespread management shake-up at the bank.
"There is no major change," Cooper said. "This is not a signal we're going to sell the bank. TCF, as we've said many times, has always been for sale if anyone wants to pay us enough. Put a different way: If anyone wants to pay us too much."
Cooper says he expects he'll have only about a 24-hour learning curve for the job, which he held for so long. He said it was natural for the TCF board to turn to him.
"When they looked around, they said, 'Let's get the guy who's already done it and knows how to do it," said Cooper. "And ask him to step in.' So, that's what I've done."
Cooper is 65 years old. But he expects to keep the CEO job for at least five years. He says he expects his compensation will be just in stock, not salary.
Stifel Nicolaus, banking analyst Ben Crabtree, says one of Cooper's major tasks will be to pump up TCF's stock price.
"I would imagine there were a lot of insiders who have a great deal of their net worth tied up in this stock, and were kind of longing for the strong hand of Bill Cooper to make things right," said Nicolaus.
While he's returning to a more prominent role on the Minnesota banking scene, Cooper says he won't be raising his political profile. He was long active in Minnesota Republican Party politics and chaired the state Republican party from 1997 to 1999.
Cooper says he's finished with any heavy-duty involvement in politics.
"I don't plan on running for party chair again or any of that kind business," he said. "In terms of people being burned out, Lynn was burned out in banking, I'm burned out in politics, I guess."
Last year, Cooper became a resident of income-tax-free Florida, complaining he was tired of Minnesota's taxes. But he says he will be re-establishing his residency in Minnesota, as the takes over as TCF's CEO.