It looks like they invested via convertible bonds -- you can see the appreciation via the "Non-Marketable Debt Securities" line in their financial statements.

It looks like they invested via convertible bonds -- you can see the appreciation via the "Non-Marketable Debt Securities" line in their financial statements. It was about $1b in 2015 after they made the investment - if you ignore other little sales/purchases, it had increased to $1.8 billion in 2017. They then note "During the year ended December 31, 2018, the terms of a non-marketable debt security were modified resulting in an unrealized $1.3 billion gain" and then the balance sheet shows a non-marketable equity security, so they must have converted at that point. The value increased by $4 billion in 2018 and another $3 billion in 2019 -- though both include other investments they'd made in private companies. By 2022, they had a total of $12 billion in unrealized gains in that category.. The majority of that is likely SpaceX so probably at minimum 10x'ed their investment?