Idaho is around the same size as Nebraska.

Nebraska is approximately 199,099 sq km, while Idaho is approximately 214,314 sq km, making Idaho 8% larger than Nebraska. Meanwhile, the population of Nebraska is ~1.8 million people (258,759 fewer people live in Idaho).
Tip: This to-scale comparison of Nebraska vs. Idaho uses the Mercator projection, which distorts the size of regions near the poles.