Fixed Income SHares Series LD Performance Management - Fixed Income SHares Series LD	Dec. 31, 2025
Prospectus [Line Items]
Bar Chart and Performance Table [Heading]	<span style="color:#00687D;font-family:Arial Narrow;font-size:12pt;font-weight:bold;">Performance Information</span>
Performance Narrative [Text Block]	The performance information shows summary performance information for the Portfolio in a bar chart and an Average Annual Total Returns table. The information provides some indication of the risks of investing in the Portfolio by showing changes in its performance from year to year and by showing how the Portfolio’s average annual total returns compare with the returns of certain indexes. Absent any applicable fee waivers and/or expense limitations, performance would have been lower. The information in the bar chart and Average Annual Total Returns Table does not reflect payment of any applicable “wrap” fees by clients of “wrap-fee” programs that invest in the Portfolio to the program sponsors. The Portfolio’s past performance, before and after taxes, is not necessarily an indication of how the Portfolio will perform in the future.In addition to the Portfolio’s performance, the Average Annual Total Returns table includes performance of: (i) a broad-based securities market index (i.e., a regulatory index) and (ii) two supplemental indexes. It is not possible to invest directly in an unmanaged index. The Portfolio’s regulatory index is the Bloomberg U.S. Aggregate Index. The Portfolio’s regulatory index is shown in connection with certain regulatory requirements to provide a broad measure of market performance. The Bloomberg U.S. Aggregate Index represents securities that are SEC-registered, taxable, and dollar denominated. The index covers the U.S. investment grade fixed rate bond market, with index components for government and corporate securities, mortgage pass-through securities, and asset-backed securities. These major sectors are subdivided into more specific indices that are calculated and reported on a regular basis. The ICE BofA 1-3 Year U.S. Treasury Index is a supplemental index of the Portfolio. The 50% ICE BofA 1-3 Year U.S. Treasury Index/50% Bloomberg U.S. Intermediate Credit Index is also a supplemental index of the Portfolio.
Performance Past Does Not Indicate Future [Text]	<span style="color:#333333;font-family:Arial Narrow;font-size:10pt;"> The Portfolio’s past performance, before and after </span><span style="color:#333333;font-family:Arial Narrow;font-size:10pt;">taxes, is not necessarily an indication of how the Portfolio will perform in the future.</span>
Performance Information Illustrates Variability of Returns [Text]	<span style="color:#333333;font-family:Arial Narrow;font-size:10pt;">The information provides some indication of the risks of investing </span><span style="color:#333333;font-family:Arial Narrow;font-size:10pt;">in the Portfolio by showing changes in its performance from year to year and by showing how the Portfolio’s average annual total returns compare with the returns of certain indexes.</span>
Performance Additional Market Index [Text]	<span style="color:#333333;font-family:Arial Narrow;font-size:10pt;">In addition to the Portfolio’s performance, the Average Annual Total Returns table includes performance of: (i) a broad-based securities market index (i.e., a regulatory index) and (ii) two supplemental indexes. It is not possible to invest directly in an unmanaged index. The Portfolio’s regulatory index is the Bloomberg U.S. Aggregate Index. The Portfolio’s regulatory index is shown in connection with certain regulatory requirements to provide a broad measure of market performance. The Bloomberg U.S. Aggregate Index represents securities that are SEC-registered, taxable, and dollar denominated. The index covers the U.S. investment grade fixed rate bond market, with index components for government and corporate securities, mortgage pass-through securities, and asset-backed securities. These major sectors are subdivided into more specific indices that are calculated and reported on a regular basis. The ICE BofA 1-3 Year U.S. Treasury Index is a supplemental index of the Portfolio. The 50% ICE BofA 1-3 Year U.S. Treasury Index/50% Bloomberg U.S. Intermediate Credit Index is also a supplemental index of the Portfolio.</span>
Bar Chart Does Not Reflect Sales Loads [Text]	<span style="color:#333333;font-family:Arial Narrow;font-size:10pt;">The information in the bar chart and Average Annual Total </span><span style="color:#333333;font-family:Arial Narrow;font-size:10pt;">Returns Table does not reflect payment of any applicable “wrap” fees by clients of “wrap-fee” programs that invest in the Portfolio to the program sponsors.</span>
Bar Chart [Heading]	<span style="color:#FFFFFF;font-family:Arial Narrow;font-size:8pt;font-weight:bold;line-height:8pt;">Calendar Year Total Returns</span>
Bar Chart Closing [Text Block]	Best QuarterJune 30, 20207.08%Worst QuarterMarch 31, 2020-3.87%
Performance Table Heading	<span style="color:#333333;font-family:Arial Narrow;font-size:10pt;font-weight:bold;">Average Annual Total Returns (for periods ended 12/31/25)</span>
Performance Table Uses Highest Federal Rate	<span style="color:#333333;font-family:Arial Narrow;font-size:8pt;">After-tax returns are calculated using the highest historical individual federal marginal income tax rates and do not reflect the impact of state and local taxes. </span>
Performance Table Not Relevant to Tax Deferred	<span style="color:#333333;font-family:Arial Narrow;font-size:8pt;">Actual after-tax </span><span style="color:#333333;font-family:Arial Narrow;font-size:8pt;">returns depend on an investor's tax situation and may differ from tax returns shown. After-tax returns are not relevant to investors who hold their shares through tax advantaged arrangements such as 401(k) plans or individual retirement accounts.</span>
Performance Table Explanation after Tax Higher	<span style="color:#333333;font-family:Arial Narrow;font-size:8pt;">In some cases the return after taxes may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Portfolio shares at the end of the measurement period.</span>
Series LD
Prospectus [Line Items]
Highest Quarterly Return, Label [Optional Text]	<span style="color:#333333;font-family:Arial Narrow;font-size:7.5pt;margin-left:0.0pt;">Best Quarter</span>
Highest Quarterly Return	7.08%
Highest Quarterly Return, Date	Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text]	<span style="color:#333333;font-family:Arial Narrow;font-size:7.5pt;margin-left:0.0pt;">Worst Quarter</span>
Lowest Quarterly Return	(3.87%)
Lowest Quarterly Return, Date	Mar. 31, 2020

Fixed Income SHares Series LD Performance Management - Fixed Income SHares Series LD

Dec. 31, 2025

Bar Chart and Performance Table [Heading]

Performance Information

The performance information shows summary performance information for the Portfolio in a bar chart and an Average Annual Total Returns table. The information provides some indication of the risks of investing in the Portfolio by showing changes in its performance from year to year and by showing how the Portfolio’s average annual total returns compare with the returns of certain indexes. Absent any applicable fee waivers and/or expense limitations, performance would have been lower. The information in the bar chart and Average Annual Total Returns Table does not reflect payment of any applicable “wrap” fees by clients of “wrap-fee” programs that invest in the Portfolio to the program sponsors. The Portfolio’s past performance, before and after taxes, is not necessarily an indication of how the Portfolio will perform in the future.In addition to the Portfolio’s performance, the Average Annual Total Returns table includes performance of: (i) a broad-based securities market index (i.e., a regulatory index) and (ii) two supplemental indexes. It is not possible to invest directly in an unmanaged index. The Portfolio’s regulatory index is the Bloomberg U.S. Aggregate Index. The Portfolio’s regulatory index is shown in connection with certain regulatory requirements to provide a broad measure of market performance. The Bloomberg U.S. Aggregate Index represents securities that are SEC-registered, taxable, and dollar denominated. The index covers the U.S. investment grade fixed rate bond market, with index components for government and corporate securities, mortgage pass-through securities, and asset-backed securities. These major sectors are subdivided into more specific indices that are calculated and reported on a regular basis. The ICE BofA 1-3 Year U.S. Treasury Index is a supplemental index of the Portfolio. The 50% ICE BofA 1-3 Year U.S. Treasury Index/50% Bloomberg U.S. Intermediate Credit Index is also a supplemental index of the Portfolio.

Performance Past Does Not Indicate Future [Text]

The Portfolio’s past performance, before and after taxes, is not necessarily an indication of how the Portfolio will perform in the future.

Performance Information Illustrates Variability of Returns [Text]

The information provides some indication of the risks of investing in the Portfolio by showing changes in its performance from year to year and by showing how the Portfolio’s average annual total returns compare with the returns of certain indexes.

Performance Additional Market Index [Text]

In addition to the Portfolio’s performance, the Average Annual Total Returns table includes performance of: (i) a broad-based securities market index (i.e., a regulatory index) and (ii) two supplemental indexes. It is not possible to invest directly in an unmanaged index. The Portfolio’s regulatory index is the Bloomberg U.S. Aggregate Index. The Portfolio’s regulatory index is shown in connection with certain regulatory requirements to provide a broad measure of market performance. The Bloomberg U.S. Aggregate Index represents securities that are SEC-registered, taxable, and dollar denominated. The index covers the U.S. investment grade fixed rate bond market, with index components for government and corporate securities, mortgage pass-through securities, and asset-backed securities. These major sectors are subdivided into more specific indices that are calculated and reported on a regular basis. The ICE BofA 1-3 Year U.S. Treasury Index is a supplemental index of the Portfolio. The 50% ICE BofA 1-3 Year U.S. Treasury Index/50% Bloomberg U.S. Intermediate Credit Index is also a supplemental index of the Portfolio.

Bar Chart Does Not Reflect Sales Loads [Text]

The information in the bar chart and Average Annual Total Returns Table does not reflect payment of any applicable “wrap” fees by clients of “wrap-fee” programs that invest in the Portfolio to the program sponsors.

Bar Chart [Heading]

Calendar Year Total Returns

Bar Chart Closing [Text Block]

Best QuarterJune 30, 20207.08%Worst QuarterMarch 31, 2020-3.87%

Performance Table Heading

Average Annual Total Returns (for periods ended 12/31/25)

Performance Table Uses Highest Federal Rate

After-tax returns are calculated using the highest historical individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

Actual after-tax returns depend on an investor's tax situation and may differ from tax returns shown. After-tax returns are not relevant to investors who hold their shares through tax advantaged arrangements such as 401(k) plans or individual retirement accounts.

Performance Table Explanation after Tax Higher

In some cases the return after taxes may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Portfolio shares at the end of the measurement period.

Series LD

Prospectus [Line Items]

Highest Quarterly Return, Label [Optional Text]

Best Quarter

Highest Quarterly Return

7.08%

Highest Quarterly Return, Date

Jun. 30, 2020

Lowest Quarterly Return, Label [Optional Text]

Worst Quarter

Lowest Quarterly Return

(3.87%)

Lowest Quarterly Return, Date

Mar. 31, 2020