Segments and Geographic Information - Revenues by Segment from Major Customers (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue, Major Customer [Line Items]
Amount	$ 1,263,460	$ 1,127,698	$ 1,169,267
AT&T Corporation [Member]
Revenue, Major Customer [Line Items]
Amount	166,401	133,090	132,674
% of Revenues	13.20%	11.80%	11.30%
Americas [Member]
Revenue, Major Customer [Line Items]
Amount	1,050,813	947,147	963,142
Americas [Member] | AT&T Corporation [Member]
Revenue, Major Customer [Line Items]
Amount	162,888	130,072	129,331
% of Revenues	12.90%	11.50%	11.10%
EMEA [Member]
Revenue, Major Customer [Line Items]
Amount	212,647	180,551	206,125
EMEA [Member] | AT&T Corporation [Member]
Revenue, Major Customer [Line Items]
Amount	$ 3,513	$ 3,018	$ 3,343
% of Revenues	0.30%	0.30%	0.20%