Summary of Significant Accounting Policies (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($) category	Jun. 30, 2019 USD ($) item	Jun. 30, 2018 USD ($) category	Nov. 08, 2017	Jul. 23, 2014
Summary Of Significant Accounting Policies [Line Items]
Interest rate					5.875%	5.875%
Operating assets independent of the Operating Partnership	$ 0		$ 0
Maximum exposure to losses	33,000,000		33,000,000
Number of Revenue Categories | category		4		4
Rental	114,977,000	$ 101,086,000	$ 224,366,000	$ 201,014,000
Useful life of property			40 years
Depreciation expense from operation	32,400,000	28,100,000	$ 62,800,000	55,000,000.0
Real estate cost capitalized excluding interest cost	4,000,000.0	3,700,000	8,500,000	7,200,000
Real estate interest cost capitalized incurred	8,400,000	6,000,000.0	16,200,000	11,400,000
Transaction cost			5,800,000
Gain on sale of real estate, net			13,408,000
Impairment losses	0		$ 0
Number of reporting units | item			1
Reclassification from Other Revenue to Rental Income [Member]
Summary Of Significant Accounting Policies [Line Items]
Prior Period Reclassification Adjustment	1,400,000		$ 4,100,000
Reclassification from Cloud and Managed Services to Other Revenue[Member]
Summary Of Significant Accounting Policies [Line Items]
Prior Period Reclassification Adjustment	11,000,000.0
Qualitytech, LP
Summary Of Significant Accounting Policies [Line Items]
Operating assets independent of the Operating Partnership	0		0
Rental	$ 114,977,000	101,086,000	224,366,000	201,014,000
Gain on sale of real estate, net			$ 13,408,000
Term Loan Maturing 2025
Summary Of Significant Accounting Policies [Line Items]
Interest rate	4.75%		4.75%
Real Estate Assets
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense from operation	$ 29,500,000	25,000,000.0	$ 57,000,000.0	48,600,000
Non-Real Estate Assets
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense from operation	2,900,000	3,100,000	5,800,000	6,400,000
Other | Reclassification from Cloud and Managed Services to Other Revenue[Member]
Summary Of Significant Accounting Policies [Line Items]
Prior Period Reclassification Adjustment			24,200,000
Other | Reclassification Other Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Prior Period Reclassification Adjustment	200,000		800,000
Recoveries From Customers
Summary Of Significant Accounting Policies [Line Items]
Prior Period Reclassification Adjustment	$ 10,400,000		$ 22,000,000.0
Minimum | Real Property
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			20 years
Maximum | Real Property
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			40 years
Maximum | Leasehold Improvements
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			20 years
Restructuring Charges [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment losses		$ 3,100,000		$ 7,100,000