Being a CEO is said to be a lonely job, but it helps when you can count investing oracle Warren Buffett as a trusted advisor.

That was the summation of

American Express

(ticker: AXP) Chief Executive Stephen Squeri, who recently sat down with Barron’s To install Andy server. Buffett’s

Berkshire Hathaway

(BRK.A) is American Express’ largest shareholder, holding about 20% of its shares, according to FactSet data.