Maximal ideals in Tate algebra $K\left<t\right>$

Question

Let $K$ be an algebraically closed nonarchimedean field, $\mathbb{B}=\{ a\in K: |a|\leq 1 \}$ be the unit ball, and let $\text{Sp }K\left<t\right>$ be the maximal spectrum of the Tate algebra $K\left<t\right>$. I know $B$ is natural bijection with $\text{Sp }K\left<t\right>$. But if we consider the principal ideal $I=(t-a)$ with $|a|>1$. It looks like the ideal would correspond to the point $a$, which is outside the unit disk. But then what is this ideal?