Link to Data:
https://www.census.gov/programs-surv...data-sets.html
Also I don't recall Twin Falls being classified as a "metro" previous to these listings. Unless I'm mistaken, it appears they have just been upgraded from a "micro" to "metro" area. The 2017 table does not list Twin Falls which appears to confirm this.
Other interesting info: Idaho's population is now at 1,754,208. If present trends continue, Idaho will surpass West Virginia (currently 1,805,832 and falling) in total population by 2020 and is quickly approaching Nebraska and New Mexico. All three of the those states have 5 electoral votes in the Electoral College and three congressional districts. They may simply drop WV's elector and give it to a different state (such as TX) but it's clear that Idaho is quickly approaching the population required to receive an additional congressional district and elector.