Stockholders' Equity - Number of Cost of Common Stock Shares Repurchased (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Common stock repurchased (in shares)	4,343	3,336	3,305
Common stock repurchased	$ 228,166	$ 161,587	$ 117,864

This element represents the value of stock that has been repurchased during the period that is held in treasury and is presented as if constructively retired. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

No definition available.

Name:	rhi_CommonStockRepurchasedValue
Namespace Prefix:	rhi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration