JPMorgan CFO: Bigger is better...for now

Each year, JPMorgan Chase's investor day serves as the company's agenda-setting town hall. It lays out its strategy for the year ahead and the benchmarks by which it will measure its success.

Past years have focused on layoffs, with an improvement in mortgage credit and a sharp slowdown in underwriting forcing the bank to eliminate some 19,000 jobs.

This year, before getting to the nitty gritty of the bank's strategy, Chief Financial Officer Marianne Lake addressed the elephant in the room: A growing debate over whether the bank, the largest in the country by assets, would need to split up.

"Our synergies are real," said Lake, pointing to a slide showing some $15 billion in revenue and $3 billion in cost savings shared by the bank due to its wide-ranging business model. Previously, JPMorgan executives had discussed synergies in the range of $6 billion to $7 billion.

Marianne Lake, chief financial officer of JPMorgan Chase & Co.
Jin Lee | Bloomberg | Getty Images
Marianne Lake, chief financial officer of JPMorgan Chase & Co.

While some of those savings would remain intact were JPMorgan to cleave its businesses into multiple parts, Lake said that it would cost far more to add capital buffers to the stand-alone units as well as corporate infrastructure.

"You'd need two finance functions, two audit functions, two risk functions, two boards, two operating committees ... and two investor days," Lake said to some laughs in the crowd. "Mortgage platforms, data centers—these are not trivial things."

Read MoreJPMorgan to close 5% of bank branches

The reason why some analysts have begun crunching the numbers, though, is due to capital. JPMorgan's massive balance sheet requires it to hold more capital than its peers, and a recent study by the Office of Financial Research found the bank to possess more risk than the other so-called systemically important financial institutions.

Some analysts, like Goldman Sachs' Richard Ramsden, have argued that, on the whole, smaller, stand-alone businesses would need to hold less capital and would be able to return more of it to shareholders.

Instead of splitting, the bank will slim down. It will discourage some financial clients from keeping their deposits at the bank, which JPMorgan says should result in a decrease in $100 billion "nonoperating" deposits (and by extension, remove the need to hold capital against that amount).

Read MoreThis is how Goldmanis doing 'God's work' now

Investment banking chief Daniel Pinto told investors he'd do "whatever it takes" to help the bank maintain—or lower—its current capital requirements.

Lake said JPMorgan would "preserve optionality" for a breakup, but the message was clear: The business model of the country's biggest bank isn't changing, at least this year.

"We've done the work ... and we've drawn our conclusion," she said.