I was able to use a level of detail calculation to find the minimum Details ID's (see below):
Please let me know if the example data has more than one detail ID per session ID, otherwise this method should work.
Next, I used an IF statement to use only the minimum detail ID (see below):
The final view in Tableau looks like this:
I hope this helps,
I forgot to mention that I was using Tableau version 9.2 for the formulas