Bug, feature request, or proposal:

If you have a longer than normal expansion panel description it overflows over the expansion panel and pushes the label out of place.

What is the expected behavior?

The description should truncate and add an ellipses, or some other way to gracefully hand this situation.

What is the current behavior?

If a description is long it will push the title out of place and overflow.

What are the steps to reproduce?

https://stackblitz.com/edit/angular-fcxlsc?file=app/expansion-overview-example.html

What is the use-case or motivation for changing an existing behavior?

It looks pretty bad if a long description is used.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Tested on Angular Material 5.2.4 using chrome 65.0.3325.181 and firefox 59.0.2.

Is there anything else we should know?

Nothing.