As you can read in Highcharts documentation:
By default (when null) the height is calculated from the offset height of the containing element, or 400 pixels if the containing element's height is 0.
So, if you didn't specify the width
value on parent element, then your chart has taken the 400px
value and set it by default.
In order to make it fits as expected, you need to define any CSS height
values on all containing elements. For example:
.col-lg-8.col-md-8.col-xs-8 {
height: 100%
}
.panel-body {
height: 94%
}
#container,
#container2 {
height: 100%
}
Live example: https://jsfiddle.net/jx46s9gn/
API Reference: https://api.highcharts.com/highcharts/chart.height