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Stock-Based Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
12 Months Ended
Apr. 28, 2012
Year
Apr. 30, 2011
Apr. 24, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Pre-tax stock-based compensation expense $ 12.6 $ 10.5 $ 8.8
After-tax stock-based compensation expense 8.4 7.2 6.2
Excess benefits 1.4 1.3 0.4
Compensation cost before income taxes related to non-vested awards yet to be recognized 23.1    
Total compensation cost expected to be recognized over a weighted average period 3.4    
Expected dividend yield 0.00%    
Expense recognized 1.6 1.7 2.0
Weighted average fair values of options granted $ 11.47 $ 14.07 $ 8.95
Weighted average remaining contractual lives of options outstanding 3.3    
Weighted average remaining contractual lives of options exercisable 2.3    
Stock options exercised, intrinsic value 1.7 4.4 3.4
Stock options exercised, cash received 5.6 6.1 3.5
Stock options exercised, tax benefits realized 0.4 1.2 1.3
Before Amendment
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Increase in the maximum number of shares that may be issued pursuant to awards of restricted stock, restricted stock awards and stock bonuses 2,000,000    
After Amendment
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Increase in the maximum number of shares that may be issued pursuant to awards of restricted stock, restricted stock awards and stock bonuses 6,000,000    
Equity Incentive Plan
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period (years) Ten    
Restricted Stock and Restricted Stock Units
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Minimum restriction period (in years) 3    
Performance-Based Awards
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period (years) Three    
Minimum restriction period (in years) 1    
Employee Stock Purchase Plan
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected dividend yield 1.40% 0.40% 0.00%
Shares of common stock reserved for issuance 4,750,000    
Expense recognized 1.8 1.8 1.6
Number of months required for eligibility to participate in plan Employees are eligible to participate after nine months of employment, if they are employed for at least 20 hours per week and more than five months per year.    
Common stock purchases represented as percentage of employee's compensation 10.00%    
Percentage of fair market value of the common stock 85.00%    
Number of shares available for purchase under stock plan 271,886    
Capital Accumulation Plan
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected dividend yield 1.40% 0.40% 0.00%
Shares of common stock reserved for issuance 6,000,000    
Expense recognized 1.3 1.4 1.6
Percentage of fair market value of the common stock 75.00%    
Number of shares available for purchase under stock plan 2,345,792    
Common stock purchases represented as percentage of employee's compensation, minimum 5.00%    
Common stock purchases represented as percentage of employee's compensation, maximum 25.00%    
Director Stock Option Plan
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Plan terminated 2002    
Vesting period (years) One    
Exercisable period, minimum One    
Exercisable period, maximum Four    
New Director Stock Option Plan
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period (years) One    
Exercisable period, minimum One    
Exercisable period, maximum Nine    
Shares of common stock reserved for issuance 800,000    
Patterson Dental Company 1992 Stock Option Plan
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares of common stock reserved for issuance 6,000,000    
Restricted Stock And Performance Unit Awards
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expense recognized 8.0 5.5 3.7
Total intrinsic value of restricted stock awards vested in period $ 4.6 $ 3.5 $ 0.8
Restricted Stock And Performance Unit Awards | Scenario 1
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period (years) Five    
Restricted Stock And Performance Unit Awards | Scenario 2
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period (years) Seven    
Restricted Stock And Performance Unit Awards | Scenario 3
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period (years) Nine    
Restricted Stock And Performance Unit Awards | Line Management
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period (years) Three    
Restricted Stock And Performance Unit Awards | Non-Employees Directors
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period (years) Three