Debt and Capital Markets (Schedule of Long-term Debt Instruments) (Details) $ in Thousands			3 Months Ended
	Apr. 05, 2017 USD ($) properties	Apr. 03, 2017 USD ($) loans properties	Mar. 31, 2017 USD ($) loans properties shares	Mar. 31, 2016 USD ($)	Apr. 06, 2017 properties	Dec. 31, 2016 shares
Debt Instrument [Line Items]
Extinguishment of Debt, Amount			$ 17,900
Number Of Mortgage Notes Receivable | loans			2
Number of Properties Securing Mortgage Note | properties			2
Common Shares, shares issued | shares			67,495,902			66,263,487
Net proceeds from issuance of common shares			$ 68,141	$ 125,199
direct share purchase plan [Member]
Debt Instrument [Line Items]
Common Shares, shares issued | shares			928,219
Net proceeds from issuance of common shares			$ 67,900
Subsequent Event [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount	$ 87,000	$ 30,200
Number Of Mortgage Notes Receivable | loans		4
Number of Properties Securing Mortgage Note | properties	11	4			14
Gain (Loss) on Extinguishment of Debt	$ 1,000