Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			40 years
Depreciation expense from operation	$ 14,100	$ 10,700	$ 26,900	$ 20,900
Real estate cost capitalized excluding interest cost	2,600	2,500	5,900	4,700
Real estate interest cost capitalized incurred	2,400	1,800	4,400	3,400
Annual amortization for intangible assets for 2015	10,900		10,900
Annual amortization for intangible assets for 2016	10,900		10,900
Amortization of the deferred financing costs			1,585	1,314
Deferred leasing costs, net	15,278		15,278		$ 16,469
Unamortized financing costs write down	100	100
In Place Leases [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of lease costs	500	600	900	1,300
Tenant Relationship [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of lease costs	600	300	900	700
Platform and Trade Names [Member]
Summary Of Significant Accounting Policies [Line Items]
Amoritzation of intangible assets	200	0	200	0
Qualitytech, LP [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of the deferred financing costs			1,585	1,314
Real Estate Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense from operation	12,400	9,100	23,300	17,900
Non-Real Estate Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense from operation	$ 1,700	$ 1,600	$ 3,600	3,000
Minimum [Member] | Real Property [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			20 years
Maximum [Member] | Real Property [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			40 years
Maximum [Member] | Leasehold Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			20 years
Unsecured Credit Facility [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of the deferred financing costs			$ 1,600	$ 1,200
Senior Notes [Member]
Summary Of Significant Accounting Policies [Line Items]
Interest rate	5.875%		5.875%
Senior notes due			2022
Princeton Facility [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred leasing costs, net					$ 2,900