Summary of Significant Accounting Policies (Narrative) (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Goodwill [Roll Forward]
Balance as of December 31, 2016				$ 752,970,000					$ 752,970,000
Merger / Acquisition									2,592,181,000
Goodwill Adjustments									(2,655,000)
Impact of Change in Foreign Exchange Rates									47,099,000
Balance as of December 31, 2017	$ 3,389,595,000				$ 752,970,000				$ 3,389,595,000	$ 752,970,000
Period in which short-term investment become cash equivalents									90 days
Interest capitalized									$ 21,700,000	16,300,000	$ 12,900,000
Compensation costs, leasing and construction activities									77,300,000	70,700,000	60,100,000
Cash flows from capitalized leasing costs									22,900,000	13,400,000	22,800,000
Deferred leasing costs, net	330,900,000				253,700,000				330,900,000	253,700,000
Gain (loss) on cash flow hedge ineffectiveness									0	(3,100,000)	(1,600,000)
Assets or liabilities for uncertain tax positions	0				0				0	0
Interest or penalties from uncertain tax positions									0	0	0
Non-cash gain on lease termination					29,200,000				0	0	14,355,000
Asset retirement obligations	12,500,000				5,700,000				$ 12,500,000	5,700,000
Number of reportable segments | segment									1
Operating revenue	731,445,000	$ 609,925,000	$ 565,989,000	550,569,000	576,787,000	$ 546,293,000	$ 514,934,000	$ 504,199,000	$ 2,457,928,000	2,142,213,000	1,763,336,000
Minimum
Goodwill [Roll Forward]
MSA term									1 year
Maximum
Goodwill [Roll Forward]
MSA term									3 years
Buildings and improvements | Minimum
Goodwill [Roll Forward]
Building and improvements, useful life									5 years
Buildings and improvements | Maximum
Goodwill [Roll Forward]
Building and improvements, useful life									39 years
Machinery and equipment | Minimum
Goodwill [Roll Forward]
Building and improvements, useful life									7 years
Machinery and equipment | Maximum
Goodwill [Roll Forward]
Building and improvements, useful life									15 years
Furniture and Fixtures | Minimum
Goodwill [Roll Forward]
Building and improvements, useful life									3 years
Furniture and Fixtures | Maximum
Goodwill [Roll Forward]
Building and improvements, useful life									5 years
United States
Goodwill [Roll Forward]
Operating revenue									$ 1,900,000,000	1,700,000,000	1,400,000,000
Long-lived assets	10,500,000,000				6,300,000,000				10,500,000,000	6,300,000,000	6,100,000,000
Non-US
Goodwill [Roll Forward]
Operating revenue									500,000,000	400,000,000	400,000,000
Long-lived assets	3,100,000,000				2,600,000,000				3,100,000,000	2,600,000,000	2,600,000,000
United Kingdom
Goodwill [Roll Forward]
Operating revenue									300,000,000	200,000,000	200,000,000
Long-lived assets	1,700,000,000				1,500,000,000				$ 1,700,000,000	$ 1,500,000,000	$ 1,600,000,000
United Kingdom | Sales
Goodwill [Roll Forward]
Concentration risk									11.20%	11.10%	12.30%
United Kingdom | Long-Lived Assets
Goodwill [Roll Forward]
Concentration risk									12.10%	16.60%	18.80%
Telx Acquisition
Goodwill [Roll Forward]
Balance as of December 31, 2016				330,845,000					$ 330,845,000
Merger / Acquisition									0
Goodwill Adjustments									0
Impact of Change in Foreign Exchange Rates									0
Balance as of December 31, 2017	330,845,000				330,845,000				330,845,000	$ 330,845,000
European Portfolio Acquisition
Goodwill [Roll Forward]
Balance as of December 31, 2016				422,125,000					422,125,000
Merger / Acquisition									0
Goodwill Adjustments									(2,620,000)
Impact of Change in Foreign Exchange Rates									47,099,000
Balance as of December 31, 2017	466,604,000				422,125,000				466,604,000	422,125,000
DFT Company
Goodwill [Roll Forward]
Balance as of December 31, 2016				$ 0					0
Merger / Acquisition									2,592,181,000
Goodwill Adjustments									(35,000)
Impact of Change in Foreign Exchange Rates									0
Balance as of December 31, 2017	$ 2,592,146,000				$ 0				$ 2,592,146,000	$ 0