Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Summary Of Significant Accounting Policies [Line Items]
Useful life of property			40 years
Depreciation expense from operation	$ 17,900	$ 11,900	$ 44,700	$ 32,800
Real estate cost capitalized excluding interest cost	2,700	2,900	8,600	7,500
Real estate interest cost capitalized incurred	2,700	1,300	7,100	4,700
Amortization of Below Market Lease	100		100
Annual amortization for intangible assets for 2015	11,000		11,000
Annual amortization for intangible assets for 2016	11,000		11,000
Amortization of the deferred financing costs			2,372	1,894
Deferred leasing costs, net	14,556		14,556		$ 16,469
Unamortized financing costs write down			100
In Place Leases [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of lease costs	400	500	1,300	1,800
Tenant Relationship [Member]
Summary Of Significant Accounting Policies [Line Items]
Amoritzation of intangible assets	2,000	300	3,000	1,000
Platform [Member]
Summary Of Significant Accounting Policies [Line Items]
Amoritzation of intangible assets	800		900
Trade Names [Member]
Summary Of Significant Accounting Policies [Line Items]
Amoritzation of intangible assets		0	300	0
Qualitytech, LP [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of the deferred financing costs			2,372	1,894
Real Estate Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense from operation	15,200	10,300	38,500	28,200
Non-Real Estate Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense from operation	$ 2,700	$ 1,600	$ 6,200	4,600
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			$ 2,400	$ 1,700
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