Executives from ACE Ltd. and Chubb are “moving quickly” and amicably to figure out the details of their $28 billion acquisition and expect their shareholders to vote on the proposal in the fall, CEO Evan Greenberg said.

“The senior leadership met for two-and-a-half days last week for integration planning purposes, and the chemistry, the optimism, the energy and the earnestness to succeed could not have been any better,” Greenberg noted during ACE’s 2015 second-quarter earnings call on July 22.

Greenberg said that both sides have launched teams to develop an integration process that covers all businesses and functional areas for both companies. They will also file an S4 regulatory form by the end of July to give an update on where they stand, after which ACE and Chubb will respectively set a date for shareholder votes – likely to be held either the end of September or October.

Additionally, Greenberg said, ACE and Chubb are preparing to file for regulatory approvals, and still expect the transaction to close by the 2016 first quarter.

“I am awfully impressed by the Chubb leadership my colleagues and I met,” Greenberg added. “They are peers.”

Since news broke that ACE would be acquiring Chubb, some industry observers have predicted more M&A activity among larger carrier. An analyst asked Greenberg during the investor call if he expected others to follow ACE/Chubb’s lead in order to achieve bigger scale. He said he expects more acquisitions, but not necessarily with a goal of greater size at the forefront.

“Most of my many competitors are very thoughtful. They are good operators. They are good stewards … of shareholders money and have a good sense of strategy for their companies,” Greenberg explained. ” Anybody that thinks that way will not look at an acquisition from the point of size, but will look at it from the intrinsic value of the thing to be acquired, and whether it is truly value-creating in a transformative way.”

“Otherwise, you don’t do something large,” said Greenberg, who will lead the combined company.

Greenberg referred to ACE’s planned acquisition of Chubb as “a very unique opportunity” that isn’t going to be repeated very often.

“We took advantage of that opportunity and I believe my colleagues who were aware of the insights behind it feel the same way about that opportunity,” Greenberg said. “When others are thinking about transformative [merger opportunities] it is not just about size. What does it bring you? [There are] not too many obvious combinations when you think that way.”

Note: Separately, ACE CEO Evan Greenberg talked about how negotiations with Chubb began, and that story can be found here.