"Detention period" refers to the time during which someone is kept or held in a specific place, typically as a form of punishment or until certain conditions are met. Full definition
He said the security services were becoming more adept at detecting threats but were then having to analyse increasingly complex information, requiring an extended detention period. (politics.co.uk)
Last week the security minister appeared to get into trouble after questioning the need to extend the 28 - day detention period for terror suspects. (politics.co.uk)