The Senate Intelligence Committee voted Thursday to declassify key pieces of a long-awaited report on the Central Intelligence Agency's interrogation program, setting in motion a process to finally make public the committee's harshly critical findings.

The panel voted 11-3 to release a 480-page executive summary and other portions of the document, but it wasn't clear how long it will take to publicly release the secret information contained in the report, which was completed in December 2012 and recently revised to incorporate...