Now, Capital One is about to test another contrarian thesis: at a time when most stand-alone credit card businesses have sold themselves to big banks, Capital One is doing the opposite and buying a midsize commercial bank.

Credit Commercial, a midsize high-quality bank available for a reasonable price, neatly fits ING's acquisition pattern and would give it a foothold in the French market, he said.

Still, banking traditions die hard here, accounting for the abundance of family institutions among midsize private banks.

Ta Chong Bank Ltd., a midsize private bank, is typical.

Currently the bank headquartered in São Paulo is one of the largest midsize banks in Brazil, and has many competitors, as Daycoval, BicBanco, Banco Pine, and others.

"It's an intriguing idea," said Alan L. McKinnon, the chief financial officer of the Bank of Boston, which has one of the largest foreign exposures among midsize banks.

But Riggs's Washington location and its international reach sometimes landed it in the middle of messes that most midsize banks elsewhere would never dream of encountering.

Consider a case filed against Citibank by SNS Bank N.V., a midsize commercial bank in the Netherlands and a Citibank client.

The Signet Banking Corporation's $81 million in loans, in connection with what seems like a scheme worthy of a detective novel, represents the largest exposure on the books of the midsize bank based in Richmond.

The new round of troubles started with anxiety about the solvency of Turkey's midsize banks.