Summary of Significant Accounting Policies (Additional Information 1) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Jun. 16, 2015	Dec. 31, 2014	Feb. 29, 2012	Feb. 08, 2012
Summary Of Significant Accounting Policies [Line Items]
Impairment losses	$ 0	$ 0	$ 0	$ 0
Goodwill	174,697		174,697
Amortization of the deferred financing costs			2,372	1,894
Written off unamortized debt cost	0
Amortization of deferred leasing costs totaled	3,100	2,500	8,600	6,700
Deferred income	25,046		25,046				$ 10,531
Amortization of deferred revenue	1,500	1,100	4,100	3,500
Company recorded equity-based compensation expense net of repurchased awards and forfeits	2,100	900	5,200	2,900
Amount of the straight-line rent receivable on the balance sheets included in rents and other receivables	7,300		7,300				$ 4,000
Unsecured Revolving Credit Facility [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of the deferred financing costs	800	500
Richmond Credit Facility [Member]
Summary Of Significant Accounting Policies [Line Items]
Written off unamortized cost related to assets securitization				100
Interest Rate Swap [Member]
Summary Of Significant Accounting Policies [Line Items]
Notional amount of derivative	$ 0		0
Derivative ineffectiveness		0		0
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Summary Of Significant Accounting Policies [Line Items]
Notional amount of derivative								$ 150,000	$ 150,000
Carpathia Hosting, Inc. [Member]
Summary Of Significant Accounting Policies [Line Items]
Goodwill					$ 175,000	$ 174,697
Unsecured Credit Facility [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of the deferred financing costs			$ 2,400	$ 1,700
Written off unamortized debt cost		500
Repayment of credit facility		$ 75,000