Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 23, 2015	Jul. 23, 2014
Summary Of Significant Accounting Policies [Line Items]
Accounts payable and accrued liabilities	$ (11,815)	$ (12,089)
Payment of minimum tax withholdings related to equity based awards	1,770	795
Proceeds from exercise of stock options	$ 42	100
Useful life of property	40 years
Depreciation expense from operation	$ 25,000	20,700
Real estate cost capitalized excluding interest cost	2,500	2,400
Real estate interest cost capitalized incurred	3,100	2,800
Qualitytech, LP [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts payable and accrued liabilities	(11,815)	(12,089)
Payment of minimum tax withholdings related to equity based awards	1,770	795
Proceeds from exercise of stock options	42	100
Real Estate Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense from operation	21,400	17,700
Non-Real Estate Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation expense from operation	$ 3,600	3,000
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
Senior Notes [Member]
Summary Of Significant Accounting Policies [Line Items]
Interest rate	5.875%		5.875%	5.875%
Cash Inflows [Member] | Accounting Standards Update 201609 [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts payable and accrued liabilities		(100)
Proceeds from exercise of stock options		100
Cash Outflows [Member] | Accounting Standards Update 201609 [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts payable and accrued liabilities		800
Payment of minimum tax withholdings related to equity based awards		$ 800