Investments in Real Estate (Acquisition - Telx) (Details) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
	Oct. 09, 2015	Oct. 08, 2015	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Consideration transferred	$ 1,886,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill			$ 752,970	$ 752,970	$ 330,664
Gain (loss) on settlement of pre-existing lease contracts			$ 29,200	0	14,355	$ 0
Transaction expenses				$ 20,491	17,400	$ 1,303
Telx Acquisition
Business Acquisition [Line Items]
Acquired entity prior years as customer	8 years
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Investments in real estate	$ 604,870
Goodwill	316,309
Above/below market lease value, net	(13,100)
Capital lease and other long-term obligations	(63,962)
Other working capital accounts and adjustments, net	47,514
Total purchase price	1,886,000
Gain (loss) on settlement of pre-existing lease contracts		$ 14,400
Write-off of deferred rent receivables		$ 75,300
Transaction expenses					$ 17,400
Telx Acquisition | Tenant relationship value
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangibles	734,800
Telx Acquisition | Acquired in-place lease value
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangibles	252,269
Telx Acquisition | Trade name
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangibles	$ 7,300