What is the economic impact of the detained immigrants at the US southern border?

Immigration, both documented and undocumented, has had a huge impact on almost every aspect of the political, social, and economic climate of USA. The current president has tried to limit immigration by increasing border security (at least at the southern border) and intensely scrutinizing asylum applications. For those who immigrated as a family, he has implemented the so-called "zero tolerance policy," where children are separated from their parents/guardians, which made headlines around the world. The policy was stopped in late June 2018. However, neither of these measures ended immigration, of course, and many immigrants still attempt to enter American soil.
The US immigration detention system is the biggest in the world, and according to several sources I've managed to find online, the country spends billions of dollars (nearly $20 billion in 2016) of the economic budget on enforcement agencies and border security. The majority of the immigrants that arrive and are often detained at the Southern Border are from the Northern Triangle countries of El Salvador, Guatemala, and Honduras, and the main reasons they choose to leave their own countries are poverty and the high crime rates. At first, the immigrants were mostly men who wanted to find better working opportunities, but now, around 60% of them are children and families.
According to the Trump administration, this has taken a toll on the economy, as it "burdened the American taxpayers" and limited the public safety. However, several studies and reports done in 2017 stated that immigrants pay nearly $12 billion dollars in taxes every year. This means that immigrants pay more taxes and take less government benefits than citizens, which in turn means that they actually have a more positive impact on the US economy, in general.
Another way these immigrants impact the economy is that, contrary to popular belief, they tend to go for jobs that most Americans wouldn't take, and they do not negatively affect American citizens' jobs or wages. In fact, if less immigrants were detained, the American workforce and birth rate would be much higher. Children would be much more productive citizens in the future if they weren't detained and were instead given citizenship.
You can find more information on the subject here.