Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Summary Of Significant Accounting Policies [Line Items]
Payment of minimum tax withholdings related to equity based awards			$ 2,464	$ 1,301
Proceeds from exercise of stock options			$ 662	666
Useful life of property			40 years
Depreciation expense from operation	$ 25,500	$ 22,600	$ 50,500	43,300
Real estate cost capitalized excluding interest cost	3,400	3,900	5,900	6,300
Real estate interest cost capitalized incurred	3,200	3,200	6,300	5,900
Qualitytech, LP [Member]
Summary Of Significant Accounting Policies [Line Items]
Payment of minimum tax withholdings related to equity based awards			2,464	1,301
Proceeds from exercise of stock options			662	666
Real Estate Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense from operation	22,000	19,500	43,400	37,200
Non-Real Estate Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense from operation	$ 3,500	$ 3,100	$ 7,100	6,100
Minimum | Real Property [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			20 years
Maximum | Real Property [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			40 years
Maximum | Leasehold Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			20 years
Cash Outflows [Member] | Accounting Standards Update 201609 [Member]
Summary Of Significant Accounting Policies [Line Items]
Payment of minimum tax withholdings related to equity based awards				700
Proceeds from exercise of stock options				$ (700)