Debt - Deferred Financing Costs (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Financing costs	$ 21,425,000		$ 20,882,000
Less: accumulated amortization	(8,518,000)		(7,972,000)
Total deferred financing costs, net	12,907,000		12,910,000
Amortization of deferred financing costs	1,300,000	$ 2,400,000
Unsecured revolving credit facility borrowings	0		35,192,000
Revolving Credit Facility | Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Unsecured revolving credit facility borrowings	0		$ 40,000,000
Deferred costs, net | Revolving Credit Facility | Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Total deferred financing costs, net	$ 4,400,000