Subsequent Events (Details) $ / shares in Units, $ in Millions			3 Months Ended
	May. 03, 2016 $ / shares	Apr. 21, 2016 USD ($) ft² property	Mar. 31, 2016 USD ($) ft² property $ / shares	Mar. 31, 2015 USD ($) ft² property
Subsequent Event [Line Items]
Number of buildings | property			149
Area of real estate property | ft²			11,100,000
Common Stock [Member]
Subsequent Event [Line Items]
Dividends Payable, Date Declared			Feb. 09, 2016
Common Stock, Dividends, Per Share, Declared | $ / shares			$ 0.180000
Dividends Payable, Date to be Paid			Apr. 12, 2016
Dividends Payable, Date of Record			Mar. 28, 2016
Common Stock [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends Payable, Date Declared	May 03, 2016
Common Stock, Dividends, Per Share, Declared | $ / shares	$ 0.18
Dividends Payable, Date to be Paid	Jul. 21, 2016
Dividends Payable, Date of Record	Jul. 07, 2016
Preferred Stock [Member]
Subsequent Event [Line Items]
Dividends Payable, Date Declared			Feb. 09, 2016
Preferred Stock, Dividends Per Share, Declared | $ / shares			$ 0.484375
Dividends Payable, Date to be Paid			Mar. 31, 2016
Dividends Payable, Date of Record			Mar. 10, 2016
Preferred Stock [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends Payable, Date Declared	May 03, 2016
Preferred Stock, Dividends Per Share, Declared | $ / shares	$ 0.484375
Dividends Payable, Date to be Paid	Jun. 30, 2016
Dividends Payable, Date of Record	Jun. 10, 2016
2016 Acquisition [Member]
Subsequent Event [Line Items]
Number of buildings | property			3
Area of real estate property | ft²			125,480
Purchase price | $			$ 27.9
2016 Acquisition [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of buildings | property		1
Area of real estate property | ft²		66,942
Purchase price | $		$ 7.4
2015 Acquisition [Member]
Subsequent Event [Line Items]
Number of buildings | property				11
Area of real estate property | ft²				1,196,322
Purchase price | $				$ 154.1