Fair Value Measurements - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
Sep. 30, 2014
Fair Value Disclosures [Abstract]
Transfers into or out of Level 1, 2 or 3 assets	$ 0

Amount of transfers of assets measured on a recurring or non-recurring basis into or out of Level 1, Level 2 or Level 3 of the fair value hierarchy into a different level.

No definition available.

Name:	kfrc_FairValueAssetTransferAmongLevelOneLevelTwoLevelThree
Namespace Prefix:	kfrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration