Idiomatic way to convert an InputStream to a String in Scala

I have a handy function that I've used in Java for converting an InputStream to a String. Here is a direct translation to Scala:

  def inputStreamToString(is: InputStream) = {
    val rd: BufferedReader = new BufferedReader(new InputStreamReader(is, "UTF-8")) 
    val builder = new StringBuilder()    
    try {
      var line = rd.readLine 
      while (line != null) { 
        builder.append(line + "\n")
        line = rd.readLine
      }
    } finally {
      rd.close
    }
    builder.toString
  }

Is there an idiomatic way to do this in scala?