Summary of Significant Accounting Policies - Goodwill and Other Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets
Amortization of Intangible Assets	$ 44,807	$ 27,940	$ 136,672	$ 78,839
Customer relationship and customer inducement intangible assets
Finite-Lived Intangible Assets
Amortization of Intangible Assets	26,782	26,889	84,401	74,299
Leases Acquired In Place and Tenant Relationships [Member]
Finite-Lived Intangible Assets
Amortization of Intangible Assets	12,036	0	30,437	0
Other finite-lived intangible assets
Finite-Lived Intangible Assets
Amortization of Intangible Assets	642	1,051	3,486	4,540
Permanent withdrawal fees
Finite-Lived Intangible Assets
Amortization of Intangible Assets	3,229	2,721	8,782	8,627
Data Center Above and Below Market Leases [Member]
Finite-Lived Intangible Assets
Amortization of Intangible Assets	$ 1,276	$ 0	$ 3,648	$ 0