Represents the number of tranches comprising the debt issuance.

No definition available.

Name:	rs_DebtInstrumentIssuedTranchesNumber
Namespace Prefix:	rs_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the lump sum amount payable at the maturity of the debt instrument.

+ References

No definition available.

+ Details

Name:	rs_DebtInstrumentPaymentAtMaturity
Namespace Prefix:	rs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the percentage of annual amortization of term loan after specified period.

+ References

No definition available.

+ Details

Name:	rs_DebtInstrumentTermLoanAnnualAmortizationPercentageAfterSpecifiedPeriod
Namespace Prefix:	rs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of annual amortization of term loan through specified period.

+ References

No definition available.

+ Details

Name:	rs_DebtInstrumentTermLoanAnnualAmortizationPercentageThroughSpecifiedPeriod
Namespace Prefix:	rs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the redemption price as a percentage of the principal amount at which the debt instrument may be required to be redeemed by the entity in the event of a change of control or downgrade of the entity's credit rating.

+ References

No definition available.

+ Details

Name:	rs_DebtRedemptionPriceDueToChangeOfControlAndDowngradeOfCreditRatingAsPercentageOfPrincipalAmount
Namespace Prefix:	rs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The contingent increase above the maximum borrowing capacity under the credit facility, if any one or more of the existing banks or new banks agree to provide such increased commitment amount.

+ References

No definition available.

+ Details

Name:	rs_LineOfCreditFacilityContingentIncreaseAdditionalBorrowingCapacity
Namespace Prefix:	rs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The number of financial covenants.

+ References

No definition available.

+ Details

Name:	rs_NumberOfFinancialCovenants
Namespace Prefix:	rs_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentDescriptionOfVariableRateBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtLongtermAndShorttermCombinedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtByMaturityAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

No definition available.

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=rs_CreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rs_UnsecuredRevolvingCreditFacilityDueSeptember2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_PrimeRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rs_UnsecuredTermLoanDueSeptember2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rs_SeniorUnsecuredNotesPubliclyTradedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rs_SeniorUnsecuredNotesIssuedNovember2006Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rs_SeniorUnsecuredNotesDueNovember2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rs_SeniorUnsecuredNotesDueNovember2036Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rs_SeniorUnsecuredNotesDue2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rs_OtherRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=rs_IndustrialRevenueBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_MortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=rs_RealEstatePropertiesPortfolioMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=rs_TravelMainHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt - Other (Details) $ in Millions		1 Months Ended		12 Months Ended
Debt - Other (Details) $ in Millions	Apr. 12, 2013 USD ($)	Sep. 30, 2016 USD ($)	Nov. 30, 2006 USD ($) tranche	Dec. 31, 2016 USD ($) item	Nov. 15, 2016 USD ($)	Dec. 31, 2015 USD ($)
Debt
Debt outstanding				$ 1,945.0		$ 1,942.1
Number of financial covenants \| item				2
Aggregate maturities of long-term debt for each of the next five years and thereafter
2017				$ 82.5
2018				38.0
2019				60.6
2020				60.6
2021				945.6
Thereafter				757.7
Total				1,945.0		1,942.1
Credit Agreement
Debt
Maximum borrowing capacity		$ 2,100.0
Debt term		5 years
Unsecured revolving credit facility due September 30, 2021
Debt
Maximum borrowing capacity		$ 1,500.0
Debt outstanding				$ 540.0		$ 332.0
Additional maximum borrowing capacity under the credit agreement subject to approval of the lenders and certain other conditions		500.0
Commitment fee on unused portion of revolving credit facility (as a percent)				0.15%
Weighted average fixed interest rate (as a percent)				2.16%		1.81%
Letters of credit outstanding				$ 62.6
Available on the revolving credit facility				897.4
Aggregate maturities of long-term debt for each of the next five years and thereafter
Total				$ 540.0		$ 332.0
Unsecured revolving credit facility due September 30, 2021 \| LIBOR
Debt
Variable interest rate				LIBOR
Interest rate added to base (as a percent)				1.25%
Unsecured revolving credit facility due September 30, 2021 \| Bank prime rate
Debt
Variable interest rate				bank prime rate
Interest rate added to base (as a percent)				0.25%
Unsecured term loan due from January 3, 2017 to September 30, 2021
Debt
Maximum borrowing capacity		$ 600.0
Debt outstanding				$ 600.0		$ 398.8
Annual amortization of term loan through September 2018 (as a percent)		5.00%
Annual amortization of term loan thereafter until June 2021 (as a percent)		10.00%
Weighted average fixed interest rate (as a percent)				2.02%		1.67%
Aggregate maturities of long-term debt for each of the next five years and thereafter
Total				$ 600.0		$ 398.8
Unsecured term loan due from January 3, 2017 to September 30, 2021 \| LIBOR
Debt
Variable interest rate				LIBOR
Interest rate added to base (as a percent)				1.25%
Unsecured term loan due from January 3, 2017 to September 30, 2021 \| Bank prime rate
Debt
Variable interest rate				bank prime rate
Interest rate added to base (as a percent)				0.25%
Senior Unsecured Notes
Debt
Percentage of principal amount at which the notes may be required to be repurchased in event of a change of control and a downgrade of the entity's credit rating				101.00%
Senior unsecured notes issued November 20, 2006
Debt
Issuance of debt			$ 600.0
Number of tranches comprising the debt issuance \| tranche			2
Senior unsecured notes due November 15, 2016
Debt
Debt outstanding						350.0
Interest rate (as a percent)			6.20%
Lump sum payment on maturity					$ 350.0
Issuance of debt			$ 350.0
Aggregate maturities of long-term debt for each of the next five years and thereafter
Total						350.0
Senior unsecured notes due November 15, 2036
Debt
Debt outstanding				$ 250.0		250.0
Interest rate (as a percent)			6.85%
Issuance of debt			$ 250.0
Aggregate maturities of long-term debt for each of the next five years and thereafter
Total				250.0		250.0
Senior unsecured notes due April 15, 2023
Debt
Debt outstanding				500.0		500.0
Interest rate (as a percent)	4.50%
Issuance of debt	$ 500.0
Aggregate maturities of long-term debt for each of the next five years and thereafter
Total				500.0		500.0
Other separate revolving credit facilities
Debt
Maximum borrowing capacity				64.9
Lines of credit				44.4		59.9
IRB
Debt
Debt outstanding				10.6		11.0
Aggregate maturities of long-term debt for each of the next five years and thereafter
Total				10.6		11.0
Mortgage obligations
Debt
Debt outstanding						$ 40.4
Interest rate (as a percent)						6.40%
Aggregate maturities of long-term debt for each of the next five years and thereafter
Total						$ 40.4
Mortgage obligations \| Real Estate Properties Portfolio
Debt
Debt outstanding				0.0
Aggregate maturities of long-term debt for each of the next five years and thereafter
Total				$ 0.0
Mortgage obligations \| Travel Main
Debt
Lump sum payment on maturity						$ 39.2