To me it would sound slightly more idiomatic (heh) to say:
Is what I have written above idiomatic?
or even, simply, if you're writing this immediately after the thing you're asking about:
Is this idiomatic?
However, that's not to say that your phrasing is wrong, per se (though I'd recommend using a comma - see examples below). You might hear, for example:
- Is he generous, then, your brother-in-law?
- Is it well paid, your new job?
- Is it far, your house, from the station?
These, though, are more common in spoken English (or written forms that more closely correspond to spoken English, like text messaging or instant messenger). For written questions on StackExchange, it sounds a bit better to use one of the two I have at the top.