A worker demonstrates Apple Pay inside a mobile kiosk sponsored by Visa and Wells Fargo to demonstrate the new Apple Pay mobile payment system on October 20, 2014 in San Francisco City.

Apple CEO Tim Cook wants the company's fastest growing business segment, Services, to double its revenue by the end of 2020.

Services, which include the App Store, iTunes, Apple Music, Apple Pay and iCloud, hit $7.17 billion in the December quarter, Apple reported during its first quarter earnings. With a growth rate of 18 percent year-over-year, services has become the fastest growing part of the business.

"We feel great about this momentum, and our goal is to double the size of the services business in the next four years," Cook said.



To put that in context, Facebook, one of the world's largest software companies, generated about $7 billion in revenue in the third quarter.



December was the App Store's best month ever, with $3 billion in sales, Cook said. The developer community — the key to Apple's sustained software success — has earned a total of $60 billion, Cook said.

The number of users of Apple Pay have tripled over the past year, Cook said on the conference call, with transaction volume up 500 percent, year over year.