The question is, why do you want idelta() on counters - or, why is increase() not suitable for your use case? What do these counters represent, and what sort of result are you looking for?
Perhaps you want to do something like this:
(foo - foo offset 2m) >= 0
This will give you the amount that metric 'foo' has increased, compared to its value 2 minutes previously. For a counter reset it will give no value, since negative values are filtered out.