Summary of Significant Accounting Policies - Goodwill and Other Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Finite-Lived Intangible Assets
Amortization of Intangible Assets	$ 47,872	$ 47,146
Customer relationship and customer inducement intangible assets
Finite-Lived Intangible Assets
Amortization of Intangible Assets	27,881	28,806
Leases Acquired In Place and Tenant Relationships [Member]
Finite-Lived Intangible Assets
Amortization of Intangible Assets	12,609	10,838
Third-party commissions asset and other finite-lived intangible assets
Finite-Lived Intangible Assets
Amortization of Intangible Assets	757	1,185
Customer inducements
Finite-Lived Intangible Assets
Amortization of Intangible Assets	2,740	2,585
Data Center Above and Below Market Leases [Member]
Finite-Lived Intangible Assets
Amortization of Intangible Assets	$ 905	$ 1,079