Hundreds of IndyMac Bancorp Inc customers descended on the company's branches on Monday to withdraw their money.
Regulators took over the Pasadena-based lender on Friday after a bank run in which customers withdrew $US1.3 billion over 11 business days.
Customers began arriving at a branch at IndyMac's headquarters on Monday at 4am - five hours before the doors opened.
The Federal Deposit Insurance Corp now operates the thrift's 33 Southern California branches.
The FDIC said the renamed IndyMac Federal Bank will cover insured deposits, mostly up to $US100,000, and initially cover 50% of uninsured deposits.
IndyMac is the fifth banking company in the United States to fail this year and the largest since the 1980s savings-and-loan crisis.
Regulators said it ended March with about $US19 billion of deposits, of which roughly $US18 billion were insured, and $US32 billion of assets.
They expect the IndyMac takeover to cost the FDIC $US4 billion to $US8 billion. The agency's insurance fund has about $US52.8 billion.
The FDIC hopes to sell IndyMac within 90 days.
