Wondering if there is a GlobalMaxTimeout setting in SiteMinder / CA Single Sign On for both ideal and max time out sessions?
It is an all or nothing switch.
A Realm timeout override cannot be combined with other individual realm Idle and Max Timeouts Realm timeout overrides (unless EnforceRealmTimeouts is used).
Unless there's a version of the Web Agent that supports the EnforceRealmTimeouts option and that option is enabled, the Idle and Max Timeouts for the user will stay at the values for the realm in which the user last authenticated (only changes if the user has to reenter credentials) (1).
To get the setting to be set up differently, create an Idea (Enhancement Request) or vote on an existing one (2).