Organization (Narrative) (Details) $ / shares in Units, ft² in Millions, $ in Millions	71 Months Ended
	Jun. 30, 2016 USD ($) ft² property $ / shares shares	Dec. 31, 2015 $ / shares shares	Sep. 22, 2014 USD ($)	Mar. 17, 2011 $ / shares shares
Operations [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Maximum amount of offering from universal shelf registration statement | $			$ 25.0
Common stock, outstanding (in shares) | shares	98,675,535	96,866,152
Proceeds from Issuance of stock | $	$ 978.4
Total real estate investments, at cost | $	$ 1,200.0
Number of real estate properties | property	35
Square Feet | ft²	7.5
Real estate property, occupancy rate	93.10%
Minimum [Member]
Operations [Line Items]
Required occupancy rate for acquisition targets	80.00%
Common Stock [Member]
Operations [Line Items]
Shares available for issuance under initial public offering (in shares) | shares				150,000,000
Common stock, par value (in dollars per share)				$ 0.01
Shares issued or available for issuance under initial public offering (in dollars per share)				10
Common Stock [Member] | Minimum [Member]
Operations [Line Items]
Shares issued or available for issuance under a distribution reinvestment plan (in dollars per share)				$ 9.50