Warren Buffett’s Berkshire Hathaway on Wednesday revealed a new, $6.72 billion stake in the insurer Chubb, confirming months of speculation that it had made a big new investment. Berkshire owned 25.92 million Chubb shares as of March 31, according to a regulatory filing detailing Berkshire’s US-listed holdings as of that date. The disclosure sent Chubb’s share price to a record high in after-hours trading, rising 6.3$268.96. Shares often rise when Berkshire reveals new holdings, reflecting what investo ...