To facilitate the massive connectivity of the 5G New Radio, this brief proposes a connectivity-scalable multiuser detector (MUD) architecture for interleave division multiple access (IDMA). A regular inter-MUD interface makes the proposed MUD not only operable alone but also scalable to serve a massive number of users by connecting multiple MUDs. Besides, the memory subsystem is simplified to mitigate the power consumption and the silicon area. A prototype 16-MUD in a 65-nm CMOS consumes 120 mW, occupies 8.21 mm2, and takes 0.16 ms to process one 8192-chip frame. Such numbers represent 29% less silicon area and 59% less power dissipation than those of the state-of-the-art MUD.