我们详细讨论了这两个话题。

We discussed both topics ___at ___length.

我们详细讨论了安排，以确保涵盖每一个细节。

We discussed the arrangements ___at ___length to ensure every detail was covered.

作者在引言中详细阐述了历史背景。

The author elaborates ___at ___length on the historical context in the introduction.