Goodwill and Acquired Intangible Assets, Net (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Goodwill and Finite-lived Intangible Assets Rollforward [Roll Forward]
Finite-Lived Intangible Assets, Net	$ 173,974	$ 158,267
Finite-Lived Intangible Assets, Amortization Expense	(17,707)
Finite-lived intangible assets, other changes	(17,083)
Goodwill	686,359	599,863
Goodwill, Other Changes	(47,584)
Intangible Assets, Net (Including Goodwill)	860,333	$ 758,130
Total intangible assets amortization expense	(17,707)
Total intangible assets, other changes	(64,667)
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	6,100
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	24,300
Finite-Lived Intangible Assets, Amortization Expense, Year Two	22,200
Finite-Lived Intangible Assets, Amortization Expense, Year Three	20,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	19,300
Finite-Lived Intangible Assets, Amortization Expense, Year Five	18,600
Finite-lived Intangible Assets Acquired	50,497
Goodwill, Acquired During Period	134,080
Total intangible assets acquired during period	$ 184,577