Nature of Business and Basis of Presentation (Details) server in Thousands, $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment country server	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of servers (more than) | server			200
Number of countries in which servers are located | country			130
Number of industry segments | segment			1
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by Operating Activities	$ 191,373	$ 435,742	$ 603,542	$ 687,590	$ 871,812	$ 793,452
Net Cash Used in Financing Activities	(116,871)	(205,025)	(314,107)	(291,088)	(359,779)	(297,029)
Adjustments for New Accounting Pronouncement [Member] | Other Current Assets [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expected cumulative effect adjustment of new accounting accounting principle in 2018			10,800
Adjustments for New Accounting Pronouncement [Member] | Other Assets [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expected cumulative effect adjustment of new accounting accounting principle in 2018			$ 23,600
As Reported [Member] | Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by Operating Activities	190,238	433,110		684,510	866,298	764,151
Net Cash Used in Financing Activities	$ (115,736)	$ (202,393)		$ (288,008)	$ (354,265)	$ (267,728)