Significant Accounting Policies (Changes in Goodwill) (Details) - USD ($)		3 Months Ended		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015		Dec. 31, 2014
Goodwill [Line Items]
Goodwill and intangible asset impairment		$ 0	$ 0
Goodwill [Roll Forward]
Beginning balance				$ 1,796,851,000		$ 1,768,949,000
Additions	[1]			166,611,000		41,011,000
Other				(740,000)		(13,109,000)
Ending balance		1,962,722,000	1,796,851,000	1,962,722,000		1,796,851,000
Enterprise and Service Provider
Goodwill [Roll Forward]
Beginning balance				1,434,369,000		1,402,156,000
Additions				61,641,000		30,317,000
Other				(740,000)	[2]	1,896,000	[3]
Ending balance		1,495,270,000	1,434,369,000	1,495,270,000		1,434,369,000
Mobility Apps division
Goodwill [Roll Forward]
Beginning balance				362,482,000		366,793,000
Additions				104,970,000		10,694,000
Other	[4]			0		(15,005,000)
Ending balance		$ 467,452,000	$ 362,482,000	$ 467,452,000		$ 362,482,000

[1] Amount primarily relates to 2015 acquisitions. See Note 3 for more information regarding the Company’s acquisitions.

[2] Amount primarily relates to adjustments to purchase price allocations for certain 2014 Acquisitions.

[3] Amount primarily relates to adjustments to purchase price allocations for certain 2013 Acquisitions.

[4] Amount primarily relates to foreign currency translation. Refer to Foreign Currency discussion below for additional information.