As artificial intelligence becomes a staple in all manner of industries, businesses will need to retrain many of their workers. Amazon has a new plan to prepare itself.

On Thursday, the Seattle-based tech giant announced it will spend $700 million to retrain 100,000 workers--more than a third of its full-time American staff--by 2025. The training will be voluntary, and aimed at either developing expertise for other jobs within Amazon--from software engineering to operations--or new careers elsewhere.

It's unclear which U.S. employees will be eligible for the initiative. Amazon did not respond to a request for clarification by the time of publication.

Employee retraining is easier said than done. Last September, business owners told Inc. about the hidden costs of such initiatives: most notably, that with the speed of technological evolution, you may never finish your retraining efforts. The programs can be expensive and time-consuming.

The announcement comes on the heels of a rash of negative news about Amazon. Earlier this month, the company lost a major federal court case, allowing it to be held liable for defective products sold through its third-party marketplace. On Monday, Bloomberg reported that Amazon workers in Minnesota plan to strike during next week's Prime Day event. And the following day, the company was summoned to testify before the U.S. House of Representatives in a hearing next week about antitrust concerns.