Detention really doesn't happen all that often with a cargo van, especially when getting unloaded. On the front end, when it happens with a cargo van, it's because the parts are still being built, or they are waiting for the freight to actually arrive. It's rare that I don't get fully paid for detention.
An illustration, though...
At Con-Way NOW, cargo van detention was $50 a half hour after one hour. Detention hardly every happened. In 3 years I think it was twice. When someone is on the hook for $100 an hour, it just didn't happen.
At Panther, cargo van detention is $15 an hour after 2 hours. Detention happens 3 or 4 times a month, because with 2 hours free and $15 an hour after that, nobody cares. After 3 hours your time is worth $5 an hour. After 4, it's $7.50 an hour. After 6 it's still only $10 an hour. They couldn't care less. And by "they" I mean whoever is paying it.
At Load One, cargo van detention is $52.50 after two hours. It happens, but not very often. Half a dozen times a year, probably, and getting paid for it has never been a problem.
The big exception is one particular shipper with an air freight warehouse in Huntsville, AL where they are fully conscious of the 2 hour free time, and will make you wait 1:59 on purpose just because they can, and will laugh about it, to your face, while they are doing it.