Simpson Thacher & Bartlett announced Thursday that corporate partner William Dougherty has been named chairman of the 837-lawyer New York–based firm’s executive committee, effective immediately.

In taking over Simpson Thacher’s top management post, the 51-year-old Dougherty succeeds corporate partner Philip "Pete" Ruegger III, 63, who has led the firm since 2004. Ruegger told The Am Law Daily Thursday that he plans to retire from full-time practice later this year after 39 years and move into an of counsel role with the firm.

Dougherty takes over as chair on the heels of a year that saw Simpson Thacher enjoy modest growth. The firm’s gross revenue rose 2 percent in 2012, to $982.5 million, according to The American Lawyer‘s reporting. Revenue per lawyer remained stable at $1.18 million, while profits per equity partner inched up slightly to $2.67 million. Last year, the firm’s revenue qualified it as the 20th highest-grossing firm on The Am Law 100—a distinction it shared with Morrison & Foerster.

Both the incoming and outgoing chairs are Simpson Thacher lifers. Dougherty joined in 1986 after graduating from the University of Chicago Law School and was promoted to partner nine years later. A private equity and mergers and acquisitions specialist, he did stints in the firm’s Tokyo and London offices before returning to New York in 2002.

Dougherty says his leadership role within the firm has "evolved" over time. Neither he nor Ruegger would discuss the mechanics of when and how Dougherty was chosen to become the new chair beyond saying the position is filled by—and from within—the firm’s 14-person executive committee. Ruegger added that he informed his fellow partners in 2010 that he planned to retire this year.

Dougherty says he expects to continue practicing, though he will no doubt have to rely on his partners to carry some of the load. According to our previous reports, Dougherty worked on a Simpson Thacher team hired by the U.S. Treasury Department in 2008 to provide outside counsel on the Trouble Asset Relief Program; worked on a 2010 transaction that saw a pair of private equity firms sell the health care business MultiPlan Inc. to another private equity consortium; and advised commercial real estate giant CB Richard Ellis in its $940 million acquisition of the real estate investment management business of Dutch insurance and financial services giant ING Group.

Dougherty, who has been a member of Simpson Thacher’s executive committee since 2008, previously chaired the firm’s new partners committee and also served as co–administrative partner from 2009 until last June. In the latter position, he helped run the firm’s day-to-day operations.

"I enjoy earning the confidence and respect of my partners," Dougherty said Thursday when asked what he likes about helping lead the firm. "I think we’ve got a fabulous institution, and I’m confident in our future."

That institution is much larger than the 693-lawyer firm Ruegger took over nine years ago. In addition to opening new offices in Washington, D.C.; Sao Paulo, Brazil; Beijing; Houston; and Seoul, Simpson Thacher also began practicing local U.K. law and local Hong Kong law under Ruegger’s watch. Along the way, Ruegger says, the firm has gone from having 16 percent of its lawyers based outside New York to having more than a third of them located beyond its home base.

"If anything we’re behind the clock," Ruegger says. "A lot of our clients probably have more of their people and activities outside New York than we do."