Fees and Expenses - iShares Securitized Income Active ETF	Apr. 30, 2025
Prospectus [Line Items]
Expense Heading [Optional Text]	Fees and Expenses
Expense Narrative [Text Block]	The following table describes the fees and expenses that you will incur if you buy, hold and sell shares of the Fund. The investment advisory agreement between BlackRock ETF Trust II (the “Trust”) and BlackRock Fund Advisors (“BFA”) (the “Investment Advisory Agreement”) provides that BFA will pay all operating expenses of the Fund, except: (i) the management fees, (ii) interest expenses, (iii) taxes, (iv) expenses incurred with respect to the acquisition and disposition of portfolio securities and the execution of portfolio transactions, including brokerage commissions, (v) distribution fees or expenses, and (vi) litigation expenses and any extraordinary expenses. The Fund may incur “Acquired Fund Fees and Expenses.” Acquired Fund Fees and Expenses reflect the Fund’s pro rata share of the fees and expenses incurred indirectly by the Fund as a result of investing in other investment companies. The impact of Acquired Fund Fees and Expenses is included in the total returns of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and Example below.
Other Expenses, New Fund, Based on Estimates [Text]	Other Expenses are based on estimated amounts for the Fund’s current fiscal year.
Operating Expenses Caption [Optional Text]	Annual Fund Operating Expenses(ongoing expenses that you pay each year as apercentage of the value of your investments)
Expense Example [Heading]	Example.
Expense Example Narrative [Text Block]	This Example is intended to help you compare the cost of owning shares of the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:
Portfolio Turnover [Heading]	Portfolio Turnover.
Portfolio Turnover [Text Block]	The Fund may pay transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in the Annual Fund OperatingExpenses or in the Example, affect the Fund’s performance. The Fund has not commenced operations as of the date of this prospectus, but it is expected that BlackRock U.S. Mortgage Portfolio, a series of Managed Account Series II (the “Predecessor Fund”), will be reorganized into the Fund. During the Predecessor Fund’s fiscal yearended April 30, 2025, the portfolio turnover rate was 285% of the average value of its portfolio.
Portfolio Turnover, Rate	285.00%

Fees and Expenses - iShares Securitized Income Active ETF

Apr. 30, 2025

Fees and Expenses

The following table describes the fees and expenses that you will incur if you buy, hold and sell shares of the Fund. The investment advisory agreement between BlackRock ETF Trust II (the “Trust”) and BlackRock Fund Advisors (“BFA”) (the “Investment Advisory Agreement”) provides that BFA will pay all operating expenses of the Fund, except: (i) the management fees, (ii) interest expenses, (iii) taxes, (iv) expenses incurred with respect to the acquisition and disposition of portfolio securities and the execution of portfolio transactions, including brokerage commissions, (v) distribution fees or expenses, and (vi) litigation expenses and any extraordinary expenses. The Fund may incur “Acquired Fund Fees and Expenses.” Acquired Fund Fees and Expenses reflect the Fund’s pro rata share of the fees and expenses incurred indirectly by the Fund as a result of investing in other investment companies. The impact of Acquired Fund Fees and Expenses is included in the total returns of the Fund.

You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and Example below.

Other Expenses, New Fund, Based on Estimates [Text]

Other Expenses are based on estimated amounts for the Fund’s current fiscal year.

Operating Expenses Caption [Optional Text]

Annual Fund Operating Expenses(ongoing expenses that you pay each year as apercentage of the value of your investments)

Expense Example [Heading]

Example.

Expense Example Narrative [Text Block]

This Example is intended to help you compare the cost of owning shares of the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

Portfolio Turnover [Heading]

Portfolio Turnover.

Portfolio Turnover [Text Block]

The Fund may pay transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in the Annual Fund OperatingExpenses or in the Example, affect the Fund’s performance. The Fund has not commenced operations as of the date of this prospectus, but it is expected that BlackRock U.S. Mortgage Portfolio, a series of Managed Account Series II (the “Predecessor Fund”), will be reorganized into the Fund. During the Predecessor Fund’s fiscal yearended April 30, 2025, the portfolio turnover rate was 285% of the average value of its portfolio.

Portfolio Turnover, Rate

285.00%