v3.26.1
Shareholder Report
 6 Months Ended
Jun. 30, 2026
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Quantitative Master Series LLC
Entity Central Index Key 0001025836
Entity Investment Company Type N-1A
Document Period End Date Jun. 30, 2026
Master Small Cap Index Series  
Shareholder Report [Line Items]  
Fund Name Master Small Cap Index Series
Class Name Master Small Cap Index Series
No Trading Symbol Flag true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Master Small Cap Index Series (the “Series”) for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Series, which is included within the iShares Russell 2000 Small-Cap Index Fund’s additional information at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441-7762.
Additional Information Phone Number (800) 441-7762
Additional Information Website blackrock.com/fundreports
Expenses [Text Block]
What were the
Series
costs for the
last six months
?
(based on a hypothetical $10,000 investment)
Series name
Costs of a $10,000
investment
Costs paid as a percentage of a
$10,000 investment
Master Small Cap Index Series
$
1		 0.02
%
(a)
(a)
Annualized.
Expenses Paid, Amount $ 1
Expense Ratio, Percent 0.02% [1]
Net Assets $ 6,001,381,204
Holdings Count | Holding 2,118
Investment Company, Portfolio Turnover 28.00%
Additional Fund Statistics [Text Block]
Key Series statistics
Net Assets
$
6,001,381,204
Number of Portfolio Holdings 2,118
Portfolio Turnover Rate 28
%
Holdings [Text Block]
What did the Series invest in?
(as of June 30, 2026)
Sector
allocation
Sector
(a)
Percent of
Net Assets
Health Care 19.8
%
Financials 17.7
%
Industrials 14.7
%
Information Technology 14.2
%
Consumer Discretionary 9.2
%
Energy 5.7
%
Real Estate 5.7
%
Materials 4.2
%
Utilities 2.7
%
Communication Services 2.4
%
Other* 2.0
%
Short-Term Securities 11.0
%
Liabilities in Excess of Other Assets (9.3
)
Ten largest holdings
Security
(b)(c)
 Percent of
Net Assets
Moog, Inc., Class A 0.4
%
Hut 8 Corp. 0.4
%
Viasat, Inc. 0.4
%
BrightSpring Health Services, Inc. 0.4
%
Cytokinetics, Inc. 0.3
%
MaxLinear, Inc. 0.3
%
Argan, Inc. 0.3
%
UMB Financial Corp. 0.3
%
JFrog Ltd. 0.3
%
Riot Platforms, Inc. 0.3
%
(a)
For purposes of this report, sector sub-classifications may differ from those utilized by the Series for compliance purposes.
(b)
Excludes underlying investments in equity swaps.
(c)
Excludes short-term securities.
*
Ten largest sectors are presented. Additional sectors are found in Other.
Largest Holdings [Text Block]
Ten largest holdings
Security
(b)(c)
 Percent of
Net Assets
Moog, Inc., Class A 0.4
%
Hut 8 Corp. 0.4
%
Viasat, Inc. 0.4
%
BrightSpring Health Services, Inc. 0.4
%
Cytokinetics, Inc. 0.3
%
MaxLinear, Inc. 0.3
%
Argan, Inc. 0.3
%
UMB Financial Corp. 0.3
%
JFrog Ltd. 0.3
%
Riot Platforms, Inc. 0.3
%
(b)
Excludes underlying investments in equity swaps.
(c)
Excludes short-term securities.
[1] Annualized.