Capital One said Thursday that it was acquiring startup Brex for $5.15 billion, the latest splashy deal undertaken by CEO Richard Fairbank.

The firm, which disclosed the deal in its fourth-quarter earnings statement, said it would pay 50% cash and 50% stock for Brex.

Shares of the bank fell about 4%.

Under Fairbank, a rare founder-CEO of a major U.S. bank, Capital One acquired rival card firm Discover Financial last year for about $35 billion.

This story is developing. Please check back for updates.