Or
\documentclass{article}
\pagestyle{empty} % for cropping
\usepackage{amsmath}
\begin{document}
\[\left|
\begin{array}{cr}
Q & \begin{matrix} 0 \\ 0 \end{matrix} \\
\begin{matrix} 2 & 3 \end{matrix} & -1
\end{array}
\right|\]
\end{document}
using the array
environment that allows a better alignment.

or maybe something like
\documentclass{article}
\pagestyle{empty} % for cropping
\usepackage{amsmath}
\usepackage{arydshln}
\begin{document}
\[ \left|
\begin{array}{c;{2pt/2pt}r}
\mbox{\LARGE $Q$} & \begin{matrix} 0 \\ 0 \end{matrix} \\ \hdashline[2pt/2pt]
\begin{matrix} 2 & 3 \end{matrix} & -1
\end{array}
\right|
\]
\end{document}
that modifies the size of Q
and includes dashed lines between columns using the arydshln
package.
