In the Google AdWords API, I believe Keyword IDs and AdGroup IDs (and obviously Campaign IDs) are unique within an account (as opposed to the Keyword ID only being unique within
Tector's answer is great--adding this because the documentation Tector links to has since been updated to clarify a point of confusion.
Globally unique entities are:
'Globally', according to the documentation, means unique across accounts.
Some of these IDs are unique on a global level across all AdWords accounts, while others are unique only within a confined scope.
From: https://developers.google.com/adwords/api/docs/guides/working-with-objects