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Intangible Assets By Major Class (Detail) (USD $)
In Thousands, unless otherwise specified
 6 Months Ended
Jun. 30, 2012
Dec. 31, 2011
Goodwill And Other Intangible Assets [Line Items]    
Finite lived intangible assets, Gross Carrying Amount $ 192,744 $ 192,846
Finite lived intangible assets, Accumulated Amortization 90,562 79,557
Intangible assets, Gross Carrying Amount 198,344 198,446
Intangible assets, Accumulated Amortization 90,562 79,557
Tradenames
    
Goodwill And Other Intangible Assets [Line Items]    
Indefinite-lived intangible assets, Useful Life Indefinite  
Indefinite-lived intangible assets, Gross Carrying Amount 5,600 5,600
Customer Relationships
    
Goodwill And Other Intangible Assets [Line Items]    
Finite lived intangible assets, Gross Carrying Amount 144,795 144,696
Finite lived intangible assets, Accumulated Amortization 56,244 49,381
Non-Competition Agreements
    
Goodwill And Other Intangible Assets [Line Items]    
Finite lived intangible assets, Gross Carrying Amount 14,395 14,601
Finite lived intangible assets, Accumulated Amortization 10,036 8,965
Software
    
Goodwill And Other Intangible Assets [Line Items]    
Finite lived intangible assets, Gross Carrying Amount 33,554 33,549
Finite lived intangible assets, Accumulated Amortization $ 24,282 $ 21,211
Minimum | Customer Relationships
    
Goodwill And Other Intangible Assets [Line Items]    
Finite lived intangible assets, Useful Life in Years 1 year  
Minimum | Non-Competition Agreements
    
Goodwill And Other Intangible Assets [Line Items]    
Finite lived intangible assets, Useful Life in Years 1 year  
Minimum | Software
    
Goodwill And Other Intangible Assets [Line Items]    
Finite lived intangible assets, Useful Life in Years 3 years  
Maximum | Customer Relationships
    
Goodwill And Other Intangible Assets [Line Items]    
Finite lived intangible assets, Useful Life in Years 15 years  
Maximum | Non-Competition Agreements
    
Goodwill And Other Intangible Assets [Line Items]    
Finite lived intangible assets, Useful Life in Years 10 years  
Maximum | Software
    
Goodwill And Other Intangible Assets [Line Items]    
Finite lived intangible assets, Useful Life in Years 6 years