W3C validation is meaningless. HTML != XML, so there isn’t any schema to validate it. No browser will choke because you added a meta element with an unregistered name. If you really are worried, you could use the data attribute on a meta element like:
<meta data-details="52:AS6[rxSdsMd4RgYXJgeabsRAVBZ:0406139009]" data-policyId="0123456789" />
at least then you know no future spec will give meaning to your data.
For more info read: http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#custom-data-attribute