Leaders of Arnold & Porter and Kaye Scholer have known one another for years, but serious discussions about a merger began within the last year, culminating in the union announced Thursday morning that creates a combined firm with close to $1 billion in annual gross revenue.

The deal, which saw partnership votes at each respective firm conclude this week, will be effective Jan. 1, 2017. Arnold & Porter Kaye Scholer will have about 1,000 lawyers, including 300 partners, spread across nine domestic and four international offices.