Berkshire Hathaway, the conglomerate controlled by billionaire investor Warren Buffett, disclosed on Wednesday its stake in Amazon was valued at $860.6m at the end of March.

Mr Buffett first revealed earlier this month that Berkshire had invested in the e-commerce giant, telling CNBC, “I’ve been a fan, and I’ve been an idiot for not buying”. Berkshire also has partnered with Amazon and JPMorgan Chase on a joint healthcare venture called Haven.

Berkshire held 483,300 Amazon shares as of the close of the first quarter, according to a 13F filing with the US Securities and Exchange Commission. It amounts to a stake of roughly 0.1 per cent in the company. Based on Amazon’s share price on Wednesday, the same investment would currently be worth $904m.

The filing also revealed that Berkshire raised its holdings in JPMorgan, Delta Air Lines and Red Hat while cutting stakes in Wells Fargo, Phillips 66, Southwest Airlines and Charter Communications.

The group’s stake in Apple remained at 249.6m shares, or 5.4 per cent, and was worth $47.4bn, its single largest investment.

Berkshire bumped up its stake in JPMorgan by 18.8 per cent to 59.5m shares, which were valued at $6bn. It owns 1.8 per cent of the bank’s shares.

Its stake in Wells Fargo, the US bank beset by scandals, narrowed by 4 per cent to 409.8m shares worth $19.8bn. Berkshire, which owns 9.1 per cent of shares, is Wells Fargo’s top shareholder.

Berkshire’s 13F filing is closely watched by investors seeking insights into the investment philosophies of Buffett and his portfolio managers Todd Combs and Ted Weschler.

Shares in Amazon were up 0.2 per cent in after-hours trading.