BMO Harris Bank added deposit dollars at the greatest rate among the 20 largest banks in the nation last quarter as it benefitted from the combination of Bank of Montreal and Harris Bank.

BMO Harris’s FDIC-insured deposit dollars last quarter grew to $33.7 billion, up 104.4% from the second quarter of 2011, according to an exclusive analysis of Federal Deposit Insurance Corp. data by Bank Innovation.

Other banks that scored big gains in new deposit dollars were JP Morgan Chase, Fifth Third Bank and Ally Bank.

Overall, the Top 20 banks in the US grew their deposit dollars by 4.4% last quarter compared to the year-previous quarter, while the number of deposit accounts fell 4.8% during that time frame. This implies that banks shed lower-balance accounts in favor of higher-ticket customers.

HSBC lost the most deposit dollars last quarter among top US banks, shedding 12.8% of its deposit assets to total nearly $45 billion of deposits. In terms of the number of deposit accounts, HSBC fared even worse, losing 30.1% of its deposit base. By quarter’s end, the number of deposit accounts in HSBC’s rolls was 2.5 million.

Rank in YOY Gains in Retail Deposits at the Top 20 Banks (*in 100s)

Bank Innovation plans to regularly publish data on FDIC-insured deposits  at the nation’s 20 largest banks by deposits as a barometer of bank customer acquisition and retention. Our reports will be published quarterly. See this tag for additional updates on deposits.