v3.26.1
Shareholder Report
 6 Months Ended
Apr. 30, 2026
USD ($)
shares
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name NICHOLAS II, INC
Entity Central Index Key 0000723455
Entity Investment Company Type N-1A
Document Period End Date Apr. 30, 2026
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
CLASS I  
Shareholder Report [Line Items]  
Fund Name Nicholas II, Inc.
Class Name Class I
Trading Symbol NCTWX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Nicholas II, Inc. (the "Fund") - Class I (the "Class") for the period of November 1, 2025 to April 30, 2026.
Additional Information [Text Block] You can find additional information about the Fund at www.nicholasfunds.com/FundMaterials. You can also request this information by contacting us at 1-800-544-6547.
Additional Information Phone Number 1-800-544-6547
Additional Information Website www.nicholasfunds.com/FundMaterials
Expenses [Text Block]
What Were the Portfolio Costs for the Last Six Months?
(based on a hypothetical $10,000 investment)
Portfolio Name Costs of a $10,000 Investment Annualized Costs Paid as a Percentage of a $10,000 Investment
Class I $29 0.60%
Expenses Paid, Amount $ 29
Expense Ratio, Percent 0.60%
Net Assets $ 880,222,932
Holdings Count | shares 68
Investment Company, Portfolio Turnover 14.76%
Additional Fund Statistics [Text Block]
Key Fund Statistics
As of April 30, 2026
Net Assets $880,222,932
Number of Portfolio Holdings 68
Portfolio Turnover Rate 14.76%
Holdings [Text Block]
Top Ten Equity Holdings
As of April 30, 2026
Name Percentage of Net Assets
Lattice Semiconductor Corporation 3.61%
Teledyne Technologies Incorporated 2.90%
AMETEK, Inc. 2.89%
Microchip Technology Incorporated 2.58%
O'Reilly Automotive, Inc. 2.51%
Corpay, Inc. 2.44%
Nordson Corporation 2.44%
CBRE Group, Inc. Class A 2.30%
Vulcan Materials Company 2.30%
IDEX Corporation 2.29%
Total of top ten 26.26%
Sector Diversification (As a Percentage of Total Investments)
As of April 30, 2026
Af Image
Largest Holdings [Text Block]
Top Ten Equity Holdings
As of April 30, 2026
Name Percentage of Net Assets
Lattice Semiconductor Corporation 3.61%
Teledyne Technologies Incorporated 2.90%
AMETEK, Inc. 2.89%
Microchip Technology Incorporated 2.58%
O'Reilly Automotive, Inc. 2.51%
Corpay, Inc. 2.44%
Nordson Corporation 2.44%
CBRE Group, Inc. Class A 2.30%
Vulcan Materials Company 2.30%
IDEX Corporation 2.29%
Total of top ten 26.26%
Class N  
Shareholder Report [Line Items]  
Fund Name Nicholas II, Inc.
Class Name Class N
Trading Symbol NNTWX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Nicholas II, Inc. (the "Fund") - Class N (the "Class") for the period of November 1, 2025 to April 30, 2026.
Additional Information [Text Block] You can find additional information about the Fund at www.nicholasfunds.com/FundMaterials. You can also request this information by contacting us at 1-800-544-6547.
Additional Information Phone Number 1-800-544-6547
Additional Information Website www.nicholasfunds.com/FundMaterials
Expenses [Text Block]
What Were the Portfolio Costs for the Last Six Months?
(based on a hypothetical $10,000 investment)
Portfolio Name Costs of a $10,000 Investment Annualized Costs Paid as a Percentage of a $10,000 Investment
Class N $44 0.91%
Expenses Paid, Amount $ 44
Expense Ratio, Percent 0.91%
Net Assets $ 880,222,932
Holdings Count | shares 68
Investment Company, Portfolio Turnover 14.76%
Additional Fund Statistics [Text Block]
Key Fund Statistics
As of April 30, 2026
Net Assets $880,222,932
Number of Portfolio Holdings 68
Portfolio Turnover Rate 14.76%
Holdings [Text Block]
Top Ten Equity Holdings
As of April 30, 2026
Name Percentage of Net Assets
Lattice Semiconductor Corporation 3.61%
Teledyne Technologies Incorporated 2.90%
AMETEK, Inc. 2.89%
Microchip Technology Incorporated 2.58%
O'Reilly Automotive, Inc. 2.51%
Corpay, Inc. 2.44%
Nordson Corporation 2.44%
CBRE Group, Inc. Class A 2.30%
Vulcan Materials Company 2.30%
IDEX Corporation 2.29%
Total of top ten 26.26%
Sector Diversification (As a Percentage of Total Investments)
As of April 30, 2026
Af Image
Largest Holdings [Text Block]
Top Ten Equity Holdings
As of April 30, 2026
Name Percentage of Net Assets
Lattice Semiconductor Corporation 3.61%
Teledyne Technologies Incorporated 2.90%
AMETEK, Inc. 2.89%
Microchip Technology Incorporated 2.58%
O'Reilly Automotive, Inc. 2.51%
Corpay, Inc. 2.44%
Nordson Corporation 2.44%
CBRE Group, Inc. Class A 2.30%
Vulcan Materials Company 2.30%
IDEX Corporation 2.29%
Total of top ten 26.26%