Use this because of the ending b;b

    <xsl:template match="invoiceDetails">
        <xsl:param name="details">
            <xsl:if test="ends-with(.,';')"><xsl:value-of
select="."/></xsl:if>
            <xsl:if test="not(ends-with(.,';'))"><xsl:value-of
select="concat(.,';')"/></xsl:if>
        </xsl:param>
        <xsl:variable name="first" select="substring-before($details,';')"/>
        <xsl:variable name="others" select="substring-after($details,';')"/>

        <xsl:if test="contains($others,';')"><xsl:value-of
select="concat(substring-before($first,'#'),';')"/></xsl:if>
        <xsl:if test="not(contains($others,';'))"><xsl:value-of
select="substring-before($first,'#')"/></xsl:if>

        <xsl:if test="contains($others,'#')">
            <xsl:apply-templates select=".">
                <xsl:with-param name="details" select="$others"/>
            </xsl:apply-templates>
        </xsl:if>
    </xsl:template>