Goodwill - Allocation of Goodwill by Reportable Segment (Detail) (USD $)
3 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Goodwill [Line Items]    
Goodwill, gross, Beginning balance $ 1,573,200,000  
Foreign exchange (2,100,000)  
Goodwill, gross, Ending balance 1,571,100,000  
Accumulated impairment charges (121,300,000)  
Goodwill, net 1,449,822,000 1,451,887,000
Wireless [Member]    
Goodwill [Line Items]    
Goodwill, gross, Beginning balance 833,100,000  
Foreign exchange (2,100,000)  
Goodwill, gross, Ending balance 831,000,000  
Accumulated impairment charges (85,100,000)  
Goodwill, net 745,900,000  
Enterprise [Member]    
Goodwill [Line Items]    
Goodwill, gross, Beginning balance   653,800,000
Goodwill, gross, Ending balance 653,800,000 653,800,000
Goodwill, net 653,800,000  
Broadband [Member]    
Goodwill [Line Items]    
Goodwill, gross, Beginning balance   86,300,000
Goodwill, gross, Ending balance 86,300,000 86,300,000
Accumulated impairment charges (36,200,000)  
Goodwill, net $ 50,100,000