Changes in Goodwill (Detail) (USD $) In Thousands, unless otherwise specified			9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Americas [Member]		Sep. 30, 2012 EMEA [Member]
Goodwill [Line Items]
Beginning Balance, Goodwill Gross	$ 205,684		$ 121,971		$ 84
Goodwill acquired during period, gross amount			80,766	[1]
Gross amount, foreign currency translation			2,863
Ending Balance, Goodwill Gross	205,684		205,600		84
Beginning Balance, Accumulated Impairment Losses	(713)		(629)		(84)
Acquisition of Alpine, accumulated impairment loss				[1]
Accumulated impairment losses, foreign currency translation
Ending Balance, Accumulated Impairment Losses	(713)		(629)		(84)
Beginning Balance, Goodwill Net	204,971	121,342	121,342
Goodwill acquired during period, net amount			80,766	[1]
Net amount, foreign currency translation			2,863
Ending Balance, Goodwill Net	$ 204,971	$ 121,342	$ 204,971

[1] See Note 2, Acquisition of Alpine Access, Inc., for further information.