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Shareholder Report
 6 Months Ended
Jun. 30, 2025
USD ($)
Holdings
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Ultra Series Fund
Entity Central Index Key 0000732697
Entity Investment Company Type N-1A
Document Period End Date Jun. 30, 2025
Conservative Allocation Fund Class I  
Shareholder Report [Line Items]  
Fund Name Conservative Allocation Fund
Class Name Conservative Allocation Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Conservative Allocation Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $17 0.33%

 

1 Annualized.
Expenses Paid, Amount $ 17
Expense Ratio, Percent 0.33% [1]
Net Assets $ 46,984,089
Holdings Count | Holdings 20
Advisory Fees Paid, Amount $ 70,831
Investment Company, Portfolio Turnover 19.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $46,984,089
# of Portfolio Holdings 20
Portfolio Turnover Rate 19%
Total Advisory Fees Paid $70,831
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Investment Companies 50.9%
Exchange Traded Funds 47.9%
Short-Term Investments 2.8%
Other Assets and Liabilities, Net (1.6%)
Exposure Basis Explanation [Text Block] The Fund invests primarily in shares of other registered investment companies. The Fund’s total net assets will be allocated among various asset classes and underlying funds with target allocations over time of approximately 35% equity investments and 65% fixed income investments.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Madison Core Bond Fund, Class R6 42.4%
Schwab Intermediate-Term U.S. Treasury ETF 8.5%
Madison Large Cap Fund, Class R6 8.5%
Janus Henderson Mortgage-Backed Securities ETF 7.8%
Invesco S&P 500 Quality ETF 6.6%
Vanguard Information Technology ETF 3.1%
Vanguard FTSE Europe ETF 2.9%
iShares MSCI Emerging Markets Asia ETF 2.6%
Vanguard Short-Term Corporate Bond ETF 2.1%
Distillate U.S. Fundamental Stability & Value ETF 2.1%
Conservative Allocation Fund Class II  
Shareholder Report [Line Items]  
Fund Name Conservative Allocation Fund
Class Name Conservative Allocation Fund Class II
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Conservative Allocation Fund Class II for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class II $29 0.58%

 

1 Annualized.
Expenses Paid, Amount $ 29
Expense Ratio, Percent 0.58% [2]
Net Assets $ 46,984,089
Holdings Count | Holdings 20
Advisory Fees Paid, Amount $ 70,831
Investment Company, Portfolio Turnover 19.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $46,984,089
# of Portfolio Holdings 20
Portfolio Turnover Rate 19%
Total Advisory Fees Paid $70,831
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Investment Companies 50.9%
Exchange Traded Funds 47.9%
Short-Term Investments 2.8%
Other Assets and Liabilities, Net (1.6%)
Exposure Basis Explanation [Text Block] The Fund invests primarily in shares of other registered investment companies. The Fund’s total net assets will be allocated among various asset classes and underlying funds with target allocations over time of approximately 35% equity investments and 65% fixed income investments.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Madison Core Bond Fund, Class R6 42.4%
Schwab Intermediate-Term U.S. Treasury ETF 8.5%
Madison Large Cap Fund, Class R6 8.5%
Janus Henderson Mortgage-Backed Securities ETF 7.8%
Invesco S&P 500 Quality ETF 6.6%
Vanguard Information Technology ETF 3.1%
Vanguard FTSE Europe ETF 2.9%
iShares MSCI Emerging Markets Asia ETF 2.6%
Vanguard Short-Term Corporate Bond ETF 2.1%
Distillate U.S. Fundamental Stability & Value ETF 2.1%
Moderate Allocation Fund Class I  
Shareholder Report [Line Items]  
Fund Name Moderate Allocation Fund
Class Name Moderate Allocation Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Moderate Allocation Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $17 0.33%

 

1 Annualized.
Expenses Paid, Amount $ 17
Expense Ratio, Percent 0.33% [3]
Net Assets $ 101,959,298
Holdings Count | Holdings 20
Advisory Fees Paid, Amount $ 153,356
Investment Company, Portfolio Turnover 25.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $101,959,298
# of Portfolio Holdings 20
Portfolio Turnover Rate 25%
Total Advisory Fees Paid $153,356
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Exchange Traded Funds 54.7%
Investment Companies 42.1%
Short-Term Investments 6.7%
Other Assets and Liabilities, Net (3.5%)
Exposure Basis Explanation [Text Block] The Fund invests primarily in shares of other registered investment companies. The Fund’s total net assets will be allocated among various asset classes and underlying funds with target allocations over time of approximately 60% equity investments and 40% fixed income investments.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Madison Core Bond Fund, Class R6 27.2%
Madison Large Cap Fund, Class R6 13.8%
Invesco S&P 500 Quality ETF 9.7%
Vanguard FTSE Europe ETF 5.5%
Vanguard Information Technology ETF 5.1%
iShares MSCI Emerging Markets Asia ETF 4.8%
Janus Henderson Mortgage-Backed Securities ETF 4.2%
Distillate U.S. Fundamental Stability & Value ETF 3.6%
iShares Core S&P Small-Cap ETF 3.2%
Schwab Intermediate-Term U.S. Treasury ETF 3.1%
Moderate Allocation Fund Class II  
Shareholder Report [Line Items]  
Fund Name Moderate Allocation Fund
Class Name Moderate Allocation Fund Class II
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Moderate Allocation Fund Class II for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class II $29 0.58%

 

1 Annualized.
Expenses Paid, Amount $ 29
Expense Ratio, Percent 0.58% [4]
Net Assets $ 101,959,298
Holdings Count | Holdings 20
Advisory Fees Paid, Amount $ 153,356
Investment Company, Portfolio Turnover 25.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $101,959,298
# of Portfolio Holdings 20
Portfolio Turnover Rate 25%
Total Advisory Fees Paid $153,356
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Exchange Traded Funds 54.7%
Investment Companies 42.1%
Short-Term Investments 6.7%
Other Assets and Liabilities, Net (3.5%)
Exposure Basis Explanation [Text Block] The Fund invests primarily in shares of other registered investment companies. The Fund’s total net assets will be allocated among various asset classes and underlying funds with target allocations over time of approximately 60% equity investments and 40% fixed income investments.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Madison Core Bond Fund, Class R6 27.2%
Madison Large Cap Fund, Class R6 13.8%
Invesco S&P 500 Quality ETF 9.7%
Vanguard FTSE Europe ETF 5.5%
Vanguard Information Technology ETF 5.1%
iShares MSCI Emerging Markets Asia ETF 4.8%
Janus Henderson Mortgage-Backed Securities ETF 4.2%
Distillate U.S. Fundamental Stability & Value ETF 3.6%
iShares Core S&P Small-Cap ETF 3.2%
Schwab Intermediate-Term U.S. Treasury ETF 3.1%
Aggressive Allocation Fund Class I  
Shareholder Report [Line Items]  
Fund Name Aggressive Allocation Fund
Class Name Aggressive Allocation Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Aggressive Allocation Fund Class I for the period of January 1, 2025 to June 30, 2025
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $17 0.32%

 

1 Annualized.
Expenses Paid, Amount $ 17
Expense Ratio, Percent 0.32% [5]
Net Assets $ 41,383,479
Holdings Count | Holdings 19
Advisory Fees Paid, Amount $ 59,918
Investment Company, Portfolio Turnover 27.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $41,383,479
# of Portfolio Holdings 19
Portfolio Turnover Rate 27%
Total Advisory Fees Paid $59,918
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Exchange Traded Funds 64.5%
Investment Companies 31.8%
Short-Term Investments 8.7%
Other Assets and Liabilities, Net (5.0%)
Exposure Basis Explanation [Text Block] The Fund invests primarily in shares of other registered investment companies. The Fund’s total net assets will be allocated among various asset classes and underlying funds with target allocations over time of approximately 80% equity investments and 20% fixed income investments.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Madison Large Cap Fund, Class R6 16.5%
Madison Core Bond Fund, Class R6 13.9%
Invesco S&P 500 Quality ETF 12.4%
Vanguard FTSE Europe ETF 8.2%
Vanguard Information Technology ETF 7.3%
Distillate U.S. Fundamental Stability & Value ETF 6.8%
iShares MSCI Emerging Markets Asia ETF 6.3%
SPDR S&P Bank ETF 4.5%
iShares Core S&P Small-Cap ETF 4.1%
Vanguard FTSE All-World ex-U.S. ETF 3.5%
Aggressive Allocation Fund Class II  
Shareholder Report [Line Items]  
Fund Name Aggressive Allocation Fund
Class Name Aggressive Allocation Fund Class II
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Aggressive Allocation Fund Class II for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class II $29 0.57%

 

1 Annualized.
Expenses Paid, Amount $ 29
Expense Ratio, Percent 0.57% [6]
Net Assets $ 41,383,479
Holdings Count | Holdings 19
Advisory Fees Paid, Amount $ 59,918
Investment Company, Portfolio Turnover 27.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $41,383,479
# of Portfolio Holdings 19
Portfolio Turnover Rate 27%
Total Advisory Fees Paid $59,918
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Exchange Traded Funds 64.5%
Investment Companies 31.8%
Short-Term Investments 8.7%
Other Assets and Liabilities, Net (5.0%)
Exposure Basis Explanation [Text Block] The Fund invests primarily in shares of other registered investment companies. The Fund’s total net assets will be allocated among various asset classes and underlying funds with target allocations over time of approximately 80% equity investments and 20% fixed income investments.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Madison Large Cap Fund, Class R6 16.5%
Madison Core Bond Fund, Class R6 13.9%
Invesco S&P 500 Quality ETF 12.4%
Vanguard FTSE Europe ETF 8.2%
Vanguard Information Technology ETF 7.3%
Distillate U.S. Fundamental Stability & Value ETF 6.8%
iShares MSCI Emerging Markets Asia ETF 6.3%
SPDR S&P Bank ETF 4.5%
iShares Core S&P Small-Cap ETF 4.1%
Vanguard FTSE All-World ex-U.S. ETF 3.5%
Diversified Income Fund Class I  
Shareholder Report [Line Items]  
Fund Name Diversified Income Fund
Class Name Diversified Income Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Diversified Income Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $14 0.27%

 

1 Annualized.
Expenses Paid, Amount $ 14
Expense Ratio, Percent 0.27% [7]
Net Assets $ 144,073,661
Holdings Count | Holdings 16
Advisory Fees Paid, Amount $ 180,875
Investment Company, Portfolio Turnover 16.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $144,073,661
# of Portfolio Holdings 16
Portfolio Turnover Rate 16%
Total Advisory Fees Paid $180,875
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Exchange Traded Funds 99.4%
Short-Term Investments 1.4%
Mortgage Backed Securities 0.0%
Commercial Mortgage-Backed Securities 0.0%
Other Assets and Liabilities, Net (0.8%)
Exposure Basis Explanation [Text Block] The Fund primarily invests in shares of other registered investment companies, diversifying across various asset classes according to an asset allocation approximately 60% in equity investments and 40% in fixed income investments.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Madison Short-Term Strategic Income ETF 22.4%
Madison Dividend Value ETF 19.0%
Madison Aggregate Bond ETF 17.9%
Madison Covered Call ETF 15.7%
SPDR Portfolio High Yield Bond ETF 10.0%
Janus Henderson Mortgage-Backed Securities ETF 4.9%
Global X MLP ETF 4.0%
Schwab U.S. Dividend Equity ETF 3.4%
iShares 5-10 Year Investment Grade Corporate Bond ETF 2.0%
Federal National Mortgage Association, 7.000%, due 11/01/31 0.0%
Diversified Income Fund Class II  
Shareholder Report [Line Items]  
Fund Name Diversified Income Fund
Class Name Diversified Income Fund Class II
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Diversified Income Fund Class II for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class II $26 0.52%

 

1 Annualized.
Expenses Paid, Amount $ 26
Expense Ratio, Percent 0.52% [8]
Net Assets $ 144,073,661
Holdings Count | Holdings 16
Advisory Fees Paid, Amount $ 180,875
Investment Company, Portfolio Turnover 16.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $144,073,661
# of Portfolio Holdings 16
Portfolio Turnover Rate 16%
Total Advisory Fees Paid $180,875
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Exchange Traded Funds 99.4%
Short-Term Investments 1.4%
Mortgage Backed Securities 0.0%
Commercial Mortgage-Backed Securities 0.0%
Other Assets and Liabilities, Net (0.8%)
Exposure Basis Explanation [Text Block] The Fund primarily invests in shares of other registered investment companies, diversifying across various asset classes according to an asset allocation approximately 60% in equity investments and 40% in fixed income investments.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Madison Short-Term Strategic Income ETF 22.4%
Madison Dividend Value ETF 19.0%
Madison Aggregate Bond ETF 17.9%
Madison Covered Call ETF 15.7%
SPDR Portfolio High Yield Bond ETF 10.0%
Janus Henderson Mortgage-Backed Securities ETF 4.9%
Global X MLP ETF 4.0%
Schwab U.S. Dividend Equity ETF 3.4%
iShares 5-10 Year Investment Grade Corporate Bond ETF 2.0%
Federal National Mortgage Association, 7.000%, due 11/01/31 0.0%
Core Bond Fund Class I  
Shareholder Report [Line Items]  
Fund Name Core Bond Fund
Class Name Core Bond Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Core Bond Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $29 0.58%

 

1 Annualized.
Expenses Paid, Amount $ 29
Expense Ratio, Percent 0.58% [9]
Net Assets $ 53,754,931
Holdings Count | Holdings 254
Advisory Fees Paid, Amount $ 172,883
Investment Company, Portfolio Turnover 8.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $53,754,931
# of Portfolio Holdings 254
Portfolio Turnover Rate 8%
Total Advisory Fees Paid $172,883
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Mortgage Backed Securities 41.1%
Corporate Notes and Bonds 25.7%
U.S. Government and Agency Obligations 18.9%
Collateralized Mortgage Obligations 6.5%
Foreign Corporate Bonds 3.1%
Short-Term Investments 2.5%
Asset Backed Securities 1.2%
Commercial Mortgage-Backed Securities 0.8%
Other Assets and Liabilities, Net 0.2%
Exposure Basis Explanation [Text Block] The Fund invests primary in fixed income securities such as Corporate, U.S. Government and Foreign debt securities. In addition the fund also invested in asset backed, mortgage-backed and commercial mortgage-backed securities.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Federal Home Loan Mortgage Corp., 2.500%, due 01/01/52 1.5%
U.S. Treasury Bonds, 6.625%, due 02/15/27 1.5%
U.S. Treasury Notes, 4.375%, due 05/15/34 1.4%
U.S. Treasury Bonds, 4.500%, due 05/15/38 1.4%
U.S. Treasury Notes, 4.000%, due 02/15/34 1.4%
U.S. Treasury Notes, 2.875%, due 05/15/28 1.4%
U.S. Treasury Notes, 2.625%, due 02/15/29 1.3%
U.S. Treasury Bonds, 4.250%, due 08/15/54 1.3%
U.S. Treasury Bonds, 3.750%, due 08/15/41 1.3%
Federal National Mortgage Association, 4.500%, due 08/01/52 1.1%
Core Bond Fund Class II  
Shareholder Report [Line Items]  
Fund Name Core Bond Fund
Class Name Core Bond Fund Class II
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Core Bond Fund Class II for the period of January 1, 2025 to June 30, 2025
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class II $42 0.83%

 

1 Annualized.
Expenses Paid, Amount $ 42
Expense Ratio, Percent 0.83% [10]
Net Assets $ 53,754,931
Holdings Count | Holdings 254
Advisory Fees Paid, Amount $ 172,883
Investment Company, Portfolio Turnover 8.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $53,754,931
# of Portfolio Holdings 254
Portfolio Turnover Rate 8%
Total Advisory Fees Paid $172,883
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Mortgage Backed Securities 41.1%
Corporate Notes and Bonds 25.7%
U.S. Government and Agency Obligations 18.9%
Collateralized Mortgage Obligations 6.5%
Foreign Corporate Bonds 3.1%
Short-Term Investments 2.5%
Asset Backed Securities 1.2%
Commercial Mortgage-Backed Securities 0.8%
Other Assets and Liabilities, Net 0.2%
Exposure Basis Explanation [Text Block] The Fund invests primary in fixed income securities such as Corporate, U.S. Government and Foreign debt securities. In addition the fund also invested in asset backed, mortgage-backed and commercial mortgage-backed securities.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Federal Home Loan Mortgage Corp., 2.500%, due 01/01/52 1.5%
U.S. Treasury Bonds, 6.625%, due 02/15/27 1.5%
U.S. Treasury Notes, 4.375%, due 05/15/34 1.4%
U.S. Treasury Bonds, 4.500%, due 05/15/38 1.4%
U.S. Treasury Notes, 4.000%, due 02/15/34 1.4%
U.S. Treasury Notes, 2.875%, due 05/15/28 1.4%
U.S. Treasury Notes, 2.625%, due 02/15/29 1.3%
U.S. Treasury Bonds, 4.250%, due 08/15/54 1.3%
U.S. Treasury Bonds, 3.750%, due 08/15/41 1.3%
Federal National Mortgage Association, 4.500%, due 08/01/52 1.1%
Large Cap Value Fund Class I  
Shareholder Report [Line Items]  
Fund Name Large Cap Value Fund
Class Name Large Cap Value Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Large Cap Value Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $32 0.63%

 

1 Annualized.
Expenses Paid, Amount $ 32
Expense Ratio, Percent 0.63% [11]
Net Assets $ 164,797,008
Holdings Count | Holdings 40
Advisory Fees Paid, Amount $ 521,825
Investment Company, Portfolio Turnover 7.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $164,797,008
# of Portfolio Holdings 40
Portfolio Turnover Rate 7%
Total Advisory Fees Paid $521,825
Holdings [Text Block]

Sector Allocation (% of Net Assets) 

Industrials 20.3%
Financials 20.0%
Health Care 14.1%
Energy 8.9%
Consumer Discretionary 8.7%
Information Technology 8.1%
Consumer Staples 7.3%
Utilities 3.6%
Equity Real Estate Investment Trusts (REITs) 2.8%
Communication Services 2.7%
Materials 1.9%
Short-Term Investments 1.6%
Other Assets and Liabilities, Net 0.0%
Exposure Basis Explanation [Text Block]

The Fund invests primarily in common stocks of large-cap companies as defined as those in the Russell 1000® Value Index. The Fund targets to maintain at least 80% of its net assets in such stocks.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

CME Group, Inc. 4.3%
Automatic Data Processing, Inc. 4.0%
Blackrock, Inc. 3.9%
Morgan Stanley 3.8%
Honeywell International, Inc. 3.8%
NextEra Energy, Inc. 3.5%
Home Depot, Inc. 3.5%
Texas Instruments, Inc. 3.5%
Johnson & Johnson 3.3%
Fastenal Co. 3.3%
Large Cap Value Fund Class II  
Shareholder Report [Line Items]  
Fund Name Large Cap Value Fund
Class Name Large Cap Value Fund Class II
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Large Cap Value Fund Class II for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class II $44 0.88%

 

1 Annualized.
Expenses Paid, Amount $ 44
Expense Ratio, Percent 0.88% [12]
Net Assets $ 164,797,008
Holdings Count | Holdings 40
Advisory Fees Paid, Amount $ 521,825
Investment Company, Portfolio Turnover 7.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $164,797,008
# of Portfolio Holdings 40
Portfolio Turnover Rate 7%
Total Advisory Fees Paid $521,825
Holdings [Text Block]

Sector Allocation (% of Net Assets) 

Industrials 20.3%
Financials 20.0%
Health Care 14.1%
Energy 8.9%
Consumer Discretionary 8.7%
Information Technology 8.1%
Consumer Staples 7.3%
Utilities 3.6%
Equity Real Estate Investment Trusts (REITs) 2.8%
Communication Services 2.7%
Materials 1.9%
Short-Term Investments 1.6%
Other Assets and Liabilities, Net 0.0%
Exposure Basis Explanation [Text Block]

The Fund invests primarily in common stocks of large-cap companies as defined as those in the Russell 1000® Value Index. The Fund targets to maintain at least 80% of its net assets in such stocks.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

CME Group, Inc. 4.3%
Automatic Data Processing, Inc. 4.0%
Blackrock, Inc. 3.9%
Morgan Stanley 3.8%
Honeywell International, Inc. 3.8%
NextEra Energy, Inc. 3.5%
Home Depot, Inc. 3.5%
Texas Instruments, Inc. 3.5%
Johnson & Johnson 3.3%
Fastenal Co. 3.3%
Large Cap Growth Fund Class I  
Shareholder Report [Line Items]  
Fund Name Large Cap Growth Fund
Class Name Large Cap Growth Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Large Cap Growth Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $41 0.83%

 

1 Annualized.
Expenses Paid, Amount $ 41
Expense Ratio, Percent 0.83% [13]
Net Assets $ 180,760,334
Holdings Count | Holdings 31
Advisory Fees Paid, Amount $ 769,153
Investment Company, Portfolio Turnover 15.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $180,760,334
# of Portfolio Holdings 31
Portfolio Turnover Rate 15%
Total Advisory Fees Paid $769,153
Holdings [Text Block]

Sector Allocation (% of Net Assets) 

Financials 26.1%
Information Technology 20.0%
Industrials 17.6%
Consumer Discretionary 15.5%
Health Care 11.7%
Communication Services 7.1%
Short-Term Investments 2.0%
Other Assets and Liabilities, Net 0.0%
Exposure Basis Explanation [Text Block]

The Fund invests primarily in common stocks of large-cap companies as defined as those in the Russell 1000® Growth Index. The Fund targets to maintain at least 80% of its net assets in such stocks.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Arch Capital Group Ltd. 6.0%
Amazon.com, Inc. 5.3%
Alphabet, Inc., Class C 5.2%
Texas Instruments, Inc. 5.0%
Ferguson Enterprises, Inc. 4.6%
Fiserv, Inc. 4.2%
Visa, Inc., Class A 3.9%
Progressive Corp. 3.8%
PACCAR, Inc. 3.8%
Parker-Hannifin Corp. 3.7%
Large Cap Growth Fund Class II  
Shareholder Report [Line Items]  
Fund Name Large Cap Growth Fund
Class Name Large Cap Growth Fund Class II
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Large Cap Growth Fund Class II for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class II $54 1.08%

 

1 Annualized.
Expenses Paid, Amount $ 54
Expense Ratio, Percent 1.08% [14]
Net Assets $ 180,760,334
Holdings Count | Holdings 31
Advisory Fees Paid, Amount $ 769,153
Investment Company, Portfolio Turnover 15.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $180,760,334
# of Portfolio Holdings 31
Portfolio Turnover Rate 15%
Total Advisory Fees Paid $769,153
Holdings [Text Block]

Sector Allocation (% of Net Assets) 

Financials 26.1%
Information Technology 20.0%
Industrials 17.6%
Consumer Discretionary 15.5%
Health Care 11.7%
Communication Services 7.1%
Short-Term Investments 2.0%
Other Assets and Liabilities, Net 0.0%
Exposure Basis Explanation [Text Block]

The Fund invests primarily in common stocks of large-cap companies as defined as those in the Russell 1000® Growth Index. The Fund targets to maintain at least 80% of its net assets in such stocks.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Arch Capital Group Ltd. 6.0%
Amazon.com, Inc. 5.3%
Alphabet, Inc., Class C 5.2%
Texas Instruments, Inc. 5.0%
Ferguson Enterprises, Inc. 4.6%
Fiserv, Inc. 4.2%
Visa, Inc., Class A 3.9%
Progressive Corp. 3.8%
PACCAR, Inc. 3.8%
Parker-Hannifin Corp. 3.7%
Mid Cap Fund Class I  
Shareholder Report [Line Items]  
Fund Name Mid Cap Fund
Class Name Mid Cap Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Mid Cap Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $46 0.93%

 

1 Annualized.
Expenses Paid, Amount $ 46
Expense Ratio, Percent 0.93% [15]
Net Assets $ 122,138,845
Holdings Count | Holdings 32
Advisory Fees Paid, Amount $ 598,960
Investment Company, Portfolio Turnover 11.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $122,138,845
# of Portfolio Holdings 32
Portfolio Turnover Rate 11%
Total Advisory Fees Paid $598,960
Holdings [Text Block]

Sector Allocation (% of Net Assets) 

Information Technology 26.0%
Financials 24.1%
Industrials 16.6%
Consumer Discretionary 14.3%
Health Care 8.0%
Communication Services 6.5%
Short-Term Investments 4.6%
Other Assets and Liabilities, Net (0.1%)
Exposure Basis Explanation [Text Block] The Fund invests in common stocks, securities convertible into common stocks and related equity securities of midsize companies defined as those companies with market capitalizations of between $500 million and $70 billion.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Arch Capital Group Ltd. 7.2%
Amphenol Corp., Class A 5.6%
Brown & Brown, Inc. 5.5%
Gartner, Inc. 5.2%
Ross Stores, Inc. 4.7%
Carlisle Cos., Inc. 4.3%
CDW Corp. 4.2%
Copart, Inc. 3.7%
PACCAR, Inc. 3.6%
Liberty Media Corp.-Liberty Formula One, Class C 3.4%
Mid Cap Fund Class II  
Shareholder Report [Line Items]  
Fund Name Mid Cap Fund
Class Name Mid Cap Fund Class II
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Mid Cap Fund Class II for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class II $59 1.18%

 

1 Annualized.
Expenses Paid, Amount $ 59
Expense Ratio, Percent 1.18% [16]
Net Assets $ 122,138,845
Holdings Count | Holdings 32
Advisory Fees Paid, Amount $ 598,960
Investment Company, Portfolio Turnover 11.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $122,138,845
# of Portfolio Holdings 32
Portfolio Turnover Rate 11%
Total Advisory Fees Paid $598,960
Holdings [Text Block]

Sector Allocation (% of Net Assets) 

Information Technology 26.0%
Financials 24.1%
Industrials 16.6%
Consumer Discretionary 14.3%
Health Care 8.0%
Communication Services 6.5%
Short-Term Investments 4.6%
Other Assets and Liabilities, Net (0.1%)
Exposure Basis Explanation [Text Block] The Fund invests in common stocks, securities convertible into common stocks and related equity securities of midsize companies defined as those companies with market capitalizations of between $500 million and $70 billion.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Arch Capital Group Ltd. 7.2%
Amphenol Corp., Class A 5.6%
Brown & Brown, Inc. 5.5%
Gartner, Inc. 5.2%
Ross Stores, Inc. 4.7%
Carlisle Cos., Inc. 4.3%
CDW Corp. 4.2%
Copart, Inc. 3.7%
PACCAR, Inc. 3.6%
Liberty Media Corp.-Liberty Formula One, Class C 3.4%
Madison Target Retirement 2020 Fund Class I  
Shareholder Report [Line Items]  
Fund Name Madison Target Retirement 2020 Fund
Class Name Madison Target Retirement 2020 Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Madison Target Retirement 2020 Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $16 0.31%

 

1 Annualized.
Expenses Paid, Amount $ 16
Expense Ratio, Percent 0.31% [17]
Net Assets $ 10,973,144
Holdings Count | Holdings 17
Advisory Fees Paid, Amount $ 14,342
Investment Company, Portfolio Turnover 9.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $10,973,144
# of Portfolio Holdings 17
Portfolio Turnover Rate 9%
Total Advisory Fees Paid $14,342
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Exchange Traded Funds 98.1%
Short-Term Investments 1.9%
Other Assets and Liabilities, Net 0.0%
Exposure Basis Explanation [Text Block] The Fund primarily invests in shares of other registered investment companies, following an asset allocation strategy for those planning to retire around 2020. As time progresses, the Fund’s allocation will shift to a more conservative mix, aiming for about 10-30% in stock funds and 70-90% in bond funds.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Janus Henderson Mortgage-Backed Securities ETF 24.1%
iShares 7-10 Year Treasury Bond ETF 16.8%
Schwab Intermediate-Term U.S. Treasury ETF 16.5%
SPDR Portfolio Short Term Treasury ETF 10.5%
iShares Aaa - A Rated Corporate Bond ETF 7.8%
Invesco S&P 500 Quality ETF 6.2%
iShares MSCI International Quality Factor ETF 3.9%
Distillate U.S. Fundamental Stability & Value ETF 3.3%
Vanguard Information Technology ETF 2.1%
SPDR Portfolio Long Term Treasury ETF 1.6%
Madison Target Retirement 2030 Fund Class I  
Shareholder Report [Line Items]  
Fund Name Madison Target Retirement 2030 Fund
Class Name Madison Target Retirement 2030 Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Madison Target Retirement 2030 Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $16 0.31%

 

1 Annualized.
Expenses Paid, Amount $ 16
Expense Ratio, Percent 0.31% [18]
Net Assets $ 50,933,863
Holdings Count | Holdings 19
Advisory Fees Paid, Amount $ 61,385
Investment Company, Portfolio Turnover 13.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $50,933,863
# of Portfolio Holdings 19
Portfolio Turnover Rate 13%
Total Advisory Fees Paid $61,385
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Exchange Traded Funds 97.0%
Short-Term Investments 3.0%
Other Assets and Liabilities, Net 0.0%
Exposure Basis Explanation [Text Block] The Fund primarily invests in shares of other registered investment companies, following an asset allocation strategy for those planning to retire around 2030. As time progresses, the Fund’s allocation will shift to a more conservative mix, aiming for about 10-30% in stock funds and 70-90% in bond funds.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Janus Henderson Mortgage-Backed Securities ETF 18.6%
iShares 7-10 Year Treasury Bond ETF 13.2%
Schwab Intermediate-Term U.S. Treasury ETF 11.7%
Invesco S&P 500 Quality ETF 10.3%
Distillate U.S. Fundamental Stability & Value ETF 8.0%
SPDR Portfolio Short Term Treasury ETF 7.9%
iShares Aaa - A Rated Corporate Bond ETF 6.1%
iShares MSCI International Quality Factor ETF 4.6%
Vanguard Information Technology ETF 3.8%
iShares MSCI Emerging Markets Asia ETF 2.4%
Madison Target Retirement 2040 Fund Class I  
Shareholder Report [Line Items]  
Fund Name Madison Target Retirement 2040 Fund
Class Name Madison Target Retirement 2040 Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Madison Target Retirement 2040 Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $16 0.31%

 

1 Annualized.
Expenses Paid, Amount $ 16
Expense Ratio, Percent 0.31% [19]
Net Assets $ 42,381,174
Holdings Count | Holdings 19
Advisory Fees Paid, Amount $ 49,619
Investment Company, Portfolio Turnover 18.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $42,381,174
# of Portfolio Holdings 19
Portfolio Turnover Rate 18%
Total Advisory Fees Paid $49,619
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Exchange Traded Funds 96.5%
Short-Term Investments 3.4%
Other Assets and Liabilities, Net 0.1%
Exposure Basis Explanation [Text Block] The Fund primarily invests in shares of other registered investment companies, following an asset allocation strategy for those planning to retire around 2040. As time progresses, the Fund’s allocation will shift to a more conservative mix, aiming for about 10-30% in stock funds and 70-90% in bond funds.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Invesco S&P 500 Quality ETF 15.4%
Distillate U.S. Fundamental Stability & Value ETF 12.9%
Janus Henderson Mortgage-Backed Securities ETF 11.0%
Schwab Intermediate-Term U.S. Treasury ETF 9.2%
iShares 7-10 Year Treasury Bond ETF 7.9%
iShares MSCI International Quality Factor ETF 7.0%
Vanguard Information Technology ETF 6.5%
iShares Aaa - A Rated Corporate Bond ETF 4.5%
iShares MSCI Emerging Markets Asia ETF 4.1%
SPDR S&P Bank ETF 3.7%
Madison Target Retirement 2050 Fund Class I  
Shareholder Report [Line Items]  
Fund Name Madison Target Retirement 2050 Fund
Class Name Madison Target Retirement 2050 Fund Class I
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Madison Target Retirement 2050 Fund Class I for the period of January 1, 2025 to June 30, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.madisonfunds.com/funds/ultra-series-fund/. You can also request this information by contacting us at 1-800-877-6089.
Additional Information Phone Number 1-800-877-6089
Additional Information Website www.madisonfunds.com/funds/ultra-series-fund/
Expenses [Text Block]

What were the Fund costs for last period? 

 

(based on a hypothetical $10,000 investment)

 

Cost of a $10,000
investment		 Costs paid as a
percentage of a
$10,000 investment1
Class I $16 0.31%

 

1 Annualized.
Expenses Paid, Amount $ 16
Expense Ratio, Percent 0.31% [20]
Net Assets $ 36,499,161
Holdings Count | Holdings 19
Advisory Fees Paid, Amount $ 42,692
Investment Company, Portfolio Turnover 19.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics (As of June 30, 2025) 

Total Net Assets $36,499,161
# of Portfolio Holdings 19
Portfolio Turnover Rate 19%
Total Advisory Fees Paid $42,692
Holdings [Text Block]

Portfolio Allocation (% of Net Assets) 

Exchange Traded Funds 96.3%
Short-Term Investments 3.6%
Other Assets and Liabilities, Net 0.1%
Exposure Basis Explanation [Text Block] The Fund primarily invests in shares of other registered investment companies, following an asset allocation strategy for those planning to retire around 2050. As time progresses, the Fund’s allocation will shift to a more conservative mix, aiming for about 10-30% in stock funds and 70-90% in bond funds.
Largest Holdings [Text Block]

Top Ten Holdings (% of Net Assets) 

Invesco S&P 500 Quality ETF 17.9%
Distillate U.S. Fundamental Stability & Value ETF 15.2%
Janus Henderson Mortgage-Backed Securities ETF 8.0%
iShares MSCI International Quality Factor ETF 7.7%
Vanguard Information Technology ETF 7.2%
Schwab Intermediate-Term U.S. Treasury ETF 6.8%
iShares 7-10 Year Treasury Bond ETF 6.1%
iShares MSCI Emerging Markets Asia ETF 4.9%
iShares MSCI Eurozone ETF 4.2%
SPDR S&P Bank ETF 4.1%
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