How much functional programming expertise can programmers be expected to have?

How much functional programming expertise can programmers be expected to
have?

I'm coding in a non-functional language with functional mechanisms (C# to
be specific, but you could substitute, say C++ and use function pointers,
or what have you) on a small team. It's my habit to use functional
techniques -- passing delegates (objects representing functions) as
arguments, using closures, occasional anonymous functions, etc -- and I
try to document this better than I think a reasonable programmer would
need them documented. Looking at code I see online and on Stack Exchange
communities, I think my style is pretty normal among C# developers.
Our team, however, isn't sophisticated in these techniques and I end up
having to explain (and defend) myself -- my high level of documentation is
actually used as evidence by them that I shouldn't code the way I do for
the sake of readability.
Now, given the make-up of my team, I understand that I might just give up
the good fight here and code to their standards, understanding its better
for the team. But, in general, is there a minimum amount of functional
programming expertise that a programmer should be able to expect of people
who are coding in a language like C#, that while not functional,
facilitates functional style?