Zions Bancorp. (ZION) and its vendor shared more details Tuesday about the company's ongoing core system conversion — a rare project, especially for financial institutions this size.

Vendor risk mitigation was the primary motivation for the project, said Zions' chief information officer, Joe Reilly. The company has eight subsidiary banks in as many states using a handful of different systems.

"With three of the four legacy systems we were using only being run by a handful of banks, we viewed that as a long-term product risk to us," Reilly said at the BAI Retail Delivery conference in Denver. "We didn't want to be one of the last banks running on a system with limited support."

The upgrade also "will provide us, out of the box, a 360-degree customer relationship view," he said.

The $54.9 billion-asset bank will begin rolling out the new technology to its branches by 2015, said Ashvini Saxena, the head of financial solutions at Tata Consultancy Services, Zions' vendor for the project.

Zions embarked on the switching process in 2010, Saxena said in an interview. Two years later, it settled on Tata as the tech vendor. By the middle of this year, Tata began work on replacing Zions' core.

Zions disclosed the plan in July, during its second-quarter earnings call. It told investors it plans to spend $200 million over the next five to seven years to make the transformation, but has said little since then.

"We've been studying this for probably a couple of years now, thoroughly vetting different alternatives and different vendors. And we have pulled the trigger to go forward on those projects," said Doyle L. Arnold, Zions' chief financial officer, on the July call.

There has been a recent flurry of core banking activity, partly due to regulatory reasons.

Many banks are going through the same thought process as Zions, says Saxena. For example, he says, some bank systems aren't equipped to handle overdraft protection. Others don't have cores that can handle remittance transfers. More still are having problems with mortgage regulation changes and legal settlements that put new demands on a bank's core.

"The regulators have been putting a lot of pressure on the banks," Saxena says. The supervisors want to know that "IT systems are sufficient and costs are controlled. They're pushing the banks to rethink their transaction systems."