Among those detained in Saudi Arabia, no name carries more power in Western financial markets than Prince Alwaleed bin Talal.

The prince, listed by Forbes as the richest Arab with $18.7 billion to his name, long has made big bets in the markets, holding major stakes in companies like Apple and CitiBank.

But his arrest now comes after Saudi Arabia hosted a major investment summit in Riyadh at one of the hotels now reportedly holding dozens of princes and former officials detained late Saturday in what authorities described as an anti-corruption campaign.

“This is going to cause some immediate apprehension in terms of investors looking at Saudi Arabia,” said Graham Griffiths, a senior analyst at Control Risks focusing on Saudi Arabia. Prince Alwaleed “is someone who has been represented as a face of the kingdom, someone that a lot of people have done business with and are comfortable doing business with.”

Prince Alwaleed, 62, is a major shareholder in Twitter, as well as an investor in ride-sharing services Lyft and Careem. He is also majority owner of the popular Rotana Group of Arabic satellite channels, and owns shares in the Four Seasons and Movenpick hotel chains.

It’s unclear how his arrest will affect global financial markets, but it is already having an effect in the ultraconservative kingdom. Shares in his Kingdom Holding Co. fell 7.5 percent in trading Sunday to 9.50 riyals ($2.53) a share, despite it announcing profits of 247.5 million riyals ($66 million) in the third quarter.

The prince has not been afraid to make big bets and lose billions, including backing then-CitiBank CEO Vikram Pandit amid the 2008 financial crisis. He earlier rescued the bank when it was CitiCorp in 1991.

“I don’t make mistakes. I make blunders,” the prince told Vanity Fair in 2013. “When you make a mistake you lose $10 million, $50 million, $100 million, but when you make a mistake of $200 million to $500 million, or $1 billion, that’s a blunder.”

But while Saudi Arabia’s King Salman and Crown Prince Mohammed bin Salman have eagerly embraced U.S. President Donald Trump, Prince Alwaleed famously criticized him during his campaign.

“You are a disgrace not only to the GOP but to all America,” the businessman tweeted in December 2015 amid the uproar over Trump’s comments about banning Muslims from traveling to the United States. “Withdraw from the U.S presidential race as you will never win.”

Trump, who once sold a yacht to the prince in 1991 and part of New York’s Plaza Hotel to him in 1995, responded by calling him “dopey” and saying he wanted to “control our U.S. politicians with daddy’s money. Can’t do it when I get elected.”

Prince Alwaleed later congratulated Trump on his electoral win.

“President elect @realDonaldTrump whatever the past differences, America has spoken,” the prince tweeted on Nov. 9, 2016.