Intangible Assets by Major Class (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Gross Carrying Amount	$ 196,171	$ 201,333
Finite lived intangible assets, Accumulated Amortization	99,913	102,752
Intangible assets, Gross Carrying Amount	201,771	206,933
Intangible assets, Accumulated Amortization	99,913	102,752
Customer Relationships
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Gross Carrying Amount	149,988	151,990
Finite lived intangible assets, Accumulated Amortization	61,774	64,095
Customer Relationships | Minimum
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Useful Life in Years	1 year
Customer Relationships | Maximum
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Useful Life in Years	15 years
Non-Competition Agreements
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Gross Carrying Amount	11,823	15,184
Finite lived intangible assets, Accumulated Amortization	9,061	11,158
Non-Competition Agreements | Minimum
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Useful Life in Years	1 year
Non-Competition Agreements | Maximum
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Useful Life in Years	10 years
Software
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Gross Carrying Amount	33,980	33,979
Finite lived intangible assets, Accumulated Amortization	28,981	27,424
Software | Minimum
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Useful Life in Years	2 years
Software | Maximum
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Useful Life in Years	10 years
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
Finite lived intangible assets, Gross Carrying Amount	380	180
Finite lived intangible assets, Accumulated Amortization	$ 97	$ 75
Tradenames | Maximum
Goodwill And Other Intangible Assets [Line Items]
Finite lived intangible assets, Useful Life in Years	2 years