While all eyes were on Bank of America’s stock price last year, the Bank of America Merrill Lynch retirement and employee financial benefit plan businesses quietly thrived by pulling in $19 billion in new financial benefit plan assets.

That was up 11% from the $17 billion in new assets that that business had in 2010. The new assets in 2011 came from new and existing relationships with companies of all sizes, according to the firm.

Kevin Crain, head of institutional retirement and benefit services at Bank of America Merrill Lynch, credits last year’s increase to the increased synergy between the firm’s designated advisor force and the commercial bank, which can help fuel new business through its existing clients.

“Over 50% of all the plans we won last year were in some way an existing commercial banking clients of the banks,” Crain said. “[That] is a pretty telling proof statement, and what I had hoped at the beginning of 2011 has actually come to fruition as the year ends.”

When broken into markets, the middle and large market client business attracted more than $12.8 billion in new assets, a 12% increase from 2010. That increase came as the firm added 368 new 401(k), defined benefit, equity and non-qualified deferred compensation plans last year.

The firm’s 401(k) business added $6.5 billion in new assets last year after adding 285 mid-to-large market 401(k) plans, marking a 17% increase from 2010.

The equity compensation and defined benefit business attracted more than $7.6 billion in equity compensation plan assets and $1.1 billion in new defined benefit plan assets.

Small to mid-sized businesses that are served through the firm’s Advisor Alliance program accounted for $4 billion in new retirement plan assets, a 26% increase from 2010. That program, which began in 2001, now has more than $26.5 billion in assets, an increase from $17 billion in early 2009.

The partnership with the commercial bank, which began about two years ago when Bank of America acquired Merrill Lynch, added $5 billion in new assets in 2011. That was up from $3.6 billion in 2010 and $700 million in 2009.

Crain credits that growth with the commercial bank to efforts the firm has made to strengthen the partnership ties, giving specialist help and carefully looking at clients. This year, the firm already has about $2 billion committed toward that business from existing bank clients, he said, and has “significant growth opportunity."

“We have tremendous growth beyond that when they have hundreds of billions of dollars of retirement plan assets that are serviced elsewhere,” Crain said.

For 2012, the firm has commitments for $8.7 billion in new assets so far from 118 new contracts from middle and large market clients.

“We keep growing very appreciably from ’09 to ’10, ’10 to ’11,” Crain said. “I would expect to be growing higher than we did in 2011 across all our business lines and then in aggregate.”

To encourage that growth, that will mean continuing to work closely with the firm’s financial advisors. That includes keeping in touch with advisors through monthly calls and annual onsite meetings.

The firm will also continue last year's efforts to expand its tools in areas such as advice, online benefits and mobile applications, Crain said.

The growth trends the retirement business saw in 2011 should continue in 2012, Crain said, in particular with the commercial bank and existing bank relationships where they have “only scratched the surface.” The commercial bank has 85,000 existing clients in the middle to large market they are targeting in retirement, he said, and hundreds of billions of dollars of retirement assets that they can try to lure in.

“I’m bullish. I can use that term as a Merrill person,” Crain said, “and I’m enthusiastic about this retirement business and where it’s going.”

Lorie Konish writes for On Wall Street.