Folks, those are USCP Detective Badges.You can clearly see, on the lady in the back, the lifted eagle and the distinct blue raised letter area (top says United States while the bottom one says Capitol Police). The normal Capitol Police badge has an olive branch under the shield so it would be noticeable. Furthermore, their lapel pins, with the capital dome on them, identify them as being members of the capital police forces.

That being said, if Nancy is being escorted by detectives, they are not there as bodyguards or police protection. It means she is either under arrest or they are simply meeting with her to question her about the stolen equipment from the Capital. However, it it were the latter, I can't see five detectives sent to question her - one or two at most maybe. A group of five, however, is usually indicative of the former.