MIAMI, Sept. 24 -- Berkshire Hathaway crossed a threshold in Lennar on Tuesday that the conglomerate had been approaching deliberately. An SEC filing disclosed that Warren Buffett's firm now holds more than 10% of the homebuilder's shares, 23.72 million Class A and 528,217 Class B in total, worth roughly $1.9 billion at Tuesday's close. The final tranche of 2.67 million Class A shares and 75,021 Class B shares was accumulated between September 17 and 21 at prices between $76.39 and $79.41 per share. Lennar stock closed Tuesday at $82.03, down 1.22%.

That discount to Tuesday's close on Berkshire's latest accumulation price tells one story. The 1.22% decline on the day, on a trading range of $81.60 to $83.30, tells another. In Texas and Fl...