Is “a glut of” well-established idiom, or simple combination of “glut” and the subsequent word?

Recently I often came across the phrase, “a glut of” as such “a glut of heroine and denial” (Reuters), “a glut of hiring alternative” (Business Week), and “a glut of foreclosed homes” (New York Times - May 23) in the following sentence:

“The nation's biggest banks and mortgage lenders have amassed a glut of foreclosed homes that threatens to deepen the housing slump”

As far as I consulted English Japanese dictionaries at hand, none of them lists “a glut of” as an idiom akin to “a lot of.” So I checked the definition of “glut” in Cambridge Dictionary Online, it simply says “a supply of something that is much greater than can be sold or is needed or wanted” but doesn’t show any reference to “a glut of.”

Is “a glut of” well-established idiom meaning abundance or excess, or simple combination of “glut” and the subsequent word?

Glut means "a lot", especially as in an overabundance of something:

glut |glət| noun an excessively abundant supply of something : there is a glut of cars on the market. [NOAD]

It is usually used to explain an economic situation, such as why house prices are down (a glut of houses on the market) or uneducated people can't find work (a glut of unskilled labor).

As hippietrail says, this is not really an idiom. But it is a well-worn phrase.

"Glut" here is just a kind of quantifier like "load" or "heap" or "pile" etc. There are tonnes of such words that are used with "of".

Glut is a bit special in its connotation of unwelcome surge being the important part rather than any specific quantity, but its use with "of" is unexceptional.

I would say that such uses of quantifier + of is idiomatic but that glut of is not an idiom.