Idiom for explaining something too thoroughly

In my shop we call this getting too deep into the weeds, which is the opposite of taking the thirty-thousand-foot view.

I'm afraid business-communications outfits like mine are sorta heirs to the Madison Avenue tradition that created gems like run it up the flagpole and see who salutes.

Labor the point

Explain or discuss something at excessive or unnecessary length.

Also known as belaboring the point.

to explain or insist on excessively. to keep explaining or insisting on to excess

example usage:

Her habit of belaboring the obvious makes her a very boring speaker.

Note US/UK variation in spelling of labor/labour.

If someone is going into too much detail one phrase is

Can't see the wood for the trees.

Which means obscuring the big picture with irrelevant detail.

In this example "wood" means "forest" and not "plank", and without this explanation the example phrase would mean the opposite!

On a different tack, repeating too much detail can be said to be

Explaining ad nauseam.

Which is a Latin term (in modern use) for an argument or discussion that has continued 'to the point of nausea'.

Overexplaining sounds like a good single-word option here. It is fairly intuitive in its meaning and is very likely to be understood by the other party even without prior knowledge of the word.

I could not find any definition or confirmation in a conventional dictionary, but an example from this online dictionary suggests your intended usage:

overexplain in British

[ˌəʊvərɪkˈspleɪn]

verb

to explain in too much detail

Wiktionary suggests a similar definition (please note that, being an open wiki, Wiktionary's information is not guaranteed to be 100% accurate, is not regarded an authoritative source and may contain accidental or deliberate errors):

Etymology

over- +‎ explain

Verb

overexplain

(third-person singular simple present overexplains, present participle overexplaining, simple past and past participle overexplained)

(transitive) To explain at unnecessary length or in too much detail.

"Going twice around the barn to get to the house" is common in Ohio where I grew up.