v3.25.2
S000004360 [Member] Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended 269 Months Ended
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
ICE BofA US Broad Market Index (Returns do not reflect deductions for fees, expenses or taxes)        
Prospectus [Line Items]        
Average Annual Return, Percent [1] 1.47% (0.34%) 1.37%  
ICE U.S. Treasury 20+ Year Bond Index (Returns do not reflect deductions for fees, expenses or taxes)        
Prospectus [Line Items]        
Average Annual Return, Percent [2] (7.71%) (5.99%) (1.04%)  
iShares 20+ Year Treasury Bond ETF        
Prospectus [Line Items]        
Average Annual Return, Percent (7.84%) (6.07%) (1.12%)  
Performance Inception Date       Jul. 22, 2002
iShares 20+ Year Treasury Bond ETF | After Taxes on Distributions        
Prospectus [Line Items]        
Average Annual Return, Percent (9.34%) (7.04%) (2.15%)  
iShares 20+ Year Treasury Bond ETF | After Taxes on Distributions and Sales        
Prospectus [Line Items]        
Average Annual Return, Percent (4.60%) (4.79%) (1.19%)  
[1] The Fund has added this broad-based index in response to new regulatory requirements.
[2] Index returns through March 31, 2016 reflect the performance of the Bloomberg U.S. 20+ Year Treasury Bond Index. Index returns from April 1, 2016 through February 28, 2021 reflect the standard pricing variant of the ICE U.S. Treasury 20+ Year Bond Index, which utilized pricing as of 3pm. Index returns from March 1, 2021 through November 30, 2023 reflect the performance of the 4pm pricing variant of the ICE U.S. Treasury 20+ Year Bond Index. Index returns beginning on December 1, 2023 reflect the performance of the standard pricing variant of the ICE U.S. Treasury 20+ Year Bond Index, which now utilizes pricing as of 4pm, and resulted in a discontinuation of the 4pm pricing variant.