Information by Segment and Geography - Narrative (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Segment Reporting [Abstract]
Percentages Of Foreign Operations Consolidated Revenue	5.00%	5.00%	5.00%	5.00%
Long lived assets of foreign operations	5.00%		5.00%		5.00%

Percentage of Long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets.

No definition available.

Name:	knx_Longlivedassetsofforeignoperations
Namespace Prefix:	knx_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	instant