Employee Benefits - Defined Contribution Plan Information (Details)	12 Months Ended
Dec. 31, 2018
Defined Contribution Plans
Eligibility period of service	3 months
Vesting percentage per year	25.00%

Represents the period of service required for employees to be eligible for participation in the defined contribution plan.

No definition available.

Name:	rs_DefinedContributionPlanRequisiteServicePeriod
Namespace Prefix:	rs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration