Subsequent Events (Details) $ / shares in Units, $ in Thousands	2 Months Ended	12 Months Ended
	Feb. 28, 2017 USD ($) Property $ / shares shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares
Subsequent Event [Line Items]
Common shares issued through public offering and direct share purchase plan during period (in shares) | shares		577,823	2,266,191	2,600,795
Proceeds from sale of property		$ 370,038	$ 156,461	$ 226,375
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of properties sold | Property	6
Proceeds from sale of real estate	$ 88,873
Number of Real Estate Properties Acquired | Property	2
Payments to acquire real estate	$ 50,594
Common shares issued through public offering and direct share purchase plan during period (in shares) | shares	1,593,603
Share price (usd per share) | $ / shares	$ 10.89
Oklahoma City, Oklahoma [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Proceeds from sale of property	$ 6,270
Proceeds from collection of loans receivable	8,498
Kennewick, Washington [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Proceeds from sale of loan receivable	$ 80,385