Image reading device and image forming apparatus including image reading device

An image reading device comprising:

• an operation unit that accepts commands from a user;
• a document transporter that transports a first document and a second document along a predetermined transport path;
• a first document reader that reads the first document having a predetermined first size and generates image data;
• a second document reader that reads the second document having a second size larger than the predetermined first size and generates image data;
• a document tilt detector that detects tilt of the second document relative to a transport direction of the predetermined transport path based on the image data for detecting the tilt of the second document;
• and
• a controller, wherein
• the controller causes the first document reader to read the first document and generate image data when the operation unit accepts a command to read the first document,
• the controller causes the first document reader to read a portion of the second document and generate image data for detecting tilt of the second document when the operation unit accepts a command to read the second document, the controller causing the document tilt detector to detect tilt of the second document relative to the transport direction of the predetermined transport path based on the image data for detecting tilt of the second document,
• the controller causes the document transporter to stop transport of the second document when the document tilt detector detects tilt of the second document, and
• the controller causes the second document reader to read the second document and generate image data when the document tilt detector detects no tilt of the second document.