Electrum as far as I know is a BIP39 wallet which uses a 2048 words dictionary while creating these 12 words seeds. The whole dictionary is available here at
https://github.com/spesmilo/electrum/blob/master/lib/wordlist/english.txt But even with 2048 words it leaves any user with atleast 2048^12 different variations. Which are quite too much to be solved by any supercomputer in upcoming years or I think decades. Someone, correct me if am wrong but I think even with the checksum there are still a total of 2048^12 variations available.
So if you go with this simple Maths. Yes electrum wallet is quite safe though for at least upcoming few decades.