idlwave-max-extra-continuation-indent

idlwave-max-extra-continuation-indent is a variable defined in `idlwave.el'.
Its value is

40

Documentation:
Maximum additional indentation for special continuation indent.
Several special indentations are tried to help line up continuation
lines in routine calls or definitions, other statements with
parentheses, or assignment statements. This variable specifies a
maximum amount by which this special indentation can exceed the
standard continuation indentation, otherwise defaulting to a fixed
offset. Set to 0 to effectively disable all special continuation
indentation, or to a large number (like 100) to enable it in all
cases. See also `idlwave-indent-to-open-paren', which can override
this variable.

You can customize this variable.