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Employee Benefit Plans - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Entity
Dec. 31, 2010
Employee Benefit Plan [Line Items]      
Percentage of every dollar of a participating employee's pre-tax contributions as matching contribution to 401(k) Plan 50.00%    
Percentage of employee's eligible compensation that represents the maximum amount of employer matching contributions to 401(K) plan 5.00%    
Percentage of every dollar of a participating employee's pre-tax contributions as matching contribution to the deferred compensation plan 50.00%    
Percentage of employee's eligible compensation that represents the maximum amount of employer matching contributions to the deferred compensation plan 5.00%    
Deferred Compensation Plan
     
Employee Benefit Plan [Line Items]      
Percentage of salary that may voluntarily be elected to be deferred 80.00%    
Percentage of bonuses, commissions and restricted stock unit grants that may voluntarily be elected to be deferred 100.00%    
Total liability for deferred compensation $ 12,541,000 $ 9,656,000  
Voluntary Savings And Investment Plan
     
Employee Benefit Plan [Line Items]      
Number of wholly-owned subsidiaries maintained voluntary savings and investment plan   3  
Total employer expenses, including employer matching contributions 3,304 2,759 2,662
GreenTeam 401(k) Plan
     
Employee Benefit Plan [Line Items]      
Percentage of every dollar of a participating employee's pre-tax contributions as matching contribution to 401(k) Plan 50.00%    
Percentage of employee's eligible compensation that represents the maximum amount of employer matching contributions to 401(K) plan 5.00%    
Alaska 401(k) Plan
     
Employee Benefit Plan [Line Items]      
Percentage of every dollar of a participating employee's pre-tax contributions as matching contribution to 401(k) Plan 100.00%    
Percentage of employee's eligible compensation that represents the maximum amount of employer matching contributions to 401(K) plan 3.00%    
R360 401(k) Plan
     
Employee Benefit Plan [Line Items]      
Percentage of every dollar of a participating employee's pre-tax contributions as matching contribution to 401(k) Plan 50.00%    
Percentage of employee's eligible compensation that represents the maximum amount of employer matching contributions to 401(K) plan 6.00%    
Multiemployer Pension Plan
     
Employee Benefit Plan [Line Items]      
Maximum percentage of contribution 5.00%    
Total employer expenses for multiemployer pension plans $ 3,812 $ 3,906 $ 3,970