Atlantic Trust, the private wealth management division of Invesco Ltd., hit a record $19.9 billion in assets under management in the third quarter of 2012, a 5% increase from the previous quarter and an 18% jump from the $16.8 billion it had in assets in the third quarter of 2011. The quarter also marks the firm’s 22nd consecutive quarter of positive net flows, the firm said in an announcement on Monday. 

“Growth is meaningful for Atlantic Trust’s clients, as it allows us to continue investing in our business, specifically our investment platform and our client service capabilities,” Jack Markwalter, chairman and CEO of Atlantic Trust, said in a statement. “It’s the steady and consistent growth of Atlantic Trust—5.5 consecutive years of positive net flows amidst uncertain financial markets—that continues to differentiate our firm from competitors.”

Most of the increase in assets came from new client inflows, David Bachert, Invesco’s media relations director, explained in an email. This year, through the end of September, the market added $763 million, or 4.2%, to assets under management, while flows added a net $1.1 billion, or 6.3%, according to Bachert.

The firm attributed its success to strong client retention, touting its 99.5% retention rate so far this year (through the end of September) among clients with more than $5 million in assets under management. Of the net flows, 63% came from new business and 37% from client additions, the firm said.

The firm does not break out revenue figures for the wealth management business, Bachert said.

Atlantic Trust operates in 11 locations throughout the U.S.