Notes Payable and Unsecured Credit Facility (Narrative) (Details) $ in Thousands		1 Months Ended	2 Months Ended	3 Months Ended
	Feb. 10, 2017 USD ($)	Jan. 30, 2017 extension	Mar. 31, 2017 USD ($) extension	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Payments on notes payable				$ 8,459	$ 34,437
Draw on unsecured credit facility				20,000	$ 50,000
Unsecured credit facility, total unencumbered pool availability			$ 514,575	514,575
Unsecured credit facility, principal amount outstanding			378,000	378,000		$ 358,000
Unsecured credit facility, amount remaining to be drawn			$ 136,575	136,575
Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Unsecured credit facility, maturity date		May 28, 2017	May 28, 2018
Unsecured credit facility, number of maturity extension periods | extension		1	2
Unsecured credit facility, available extension period		12 months	12 months
Unsecured credit facility, principal amount outstanding			$ 168,000	$ 168,000		$ 148,000
Note Payable One [Member]
Debt Instrument [Line Items]
Notes payable, maturity date	Feb. 10, 2017
Payments on notes payable	$ 5,645