How to automatically have larger "|“ symbol

[Yingky]

I usually need to write something like
\begin{align*}
|\sum\limits a_{n}| , |\int f(x) , dx |
\end{align*}

I want to automatically make symbol “|” larger when the sum or integral is in “| |”

So far, I can only type “\bigg” in front of “|” to enlarge the symbol. Any help? Thanks!

[JayKim]

With \left| and \right|

\begin{align*}
\left| \sum\limits a_{n} \right| , \left| \int f(x) , dx \right|
\end{align*}