Notes Payable to Trusts - Additional Information (Details)	1 Months Ended			12 Months Ended	60 Months Ended	61 Months Ended
	Jul. 31, 2005 USD ($) Security	May 31, 2005 USD ($) Security	Apr. 30, 2005 USD ($) Security	Dec. 31, 2017 USD ($)	Jun. 30, 2010	Jul. 31, 2010	Dec. 31, 2016 USD ($)	Jul. 11, 2011
Variable Interest Entity [Line Items]
Unamortized deferred financing costs, net				$ 2,146,000			$ 2,269,000
Variable Interest Entity, Not Primary Beneficiary | Trust III
Variable Interest Entity [Line Items]
Proceeds from issuance of securities	$ 41,238,000
Variable Interest Entity, Not Primary Beneficiary | Trust III | Preferred Securities
Variable Interest Entity [Line Items]
Issuance of securities	40,000,000
Variable Interest Entity, Not Primary Beneficiary | Trust III | Common Securities
Variable Interest Entity [Line Items]
Issuance of securities	$ 1,238,000
Number of securities issued (in securities) | Security	1,238
Variable Interest Entity, Not Primary Beneficiary | Trust II
Variable Interest Entity [Line Items]
Proceeds from issuance of securities		$ 42,269,000
Variable Interest Entity, Not Primary Beneficiary | Trust II | Preferred Securities
Variable Interest Entity [Line Items]
Issuance of securities		41,000,000
Variable Interest Entity, Not Primary Beneficiary | Trust II | Common Securities
Variable Interest Entity [Line Items]
Issuance of securities		$ 1,269,000
Number of securities issued (in securities) | Security		1,269
Variable Interest Entity, Not Primary Beneficiary | Trust
Variable Interest Entity [Line Items]
Proceeds from issuance of securities			$ 36,083,000
Variable Interest Entity, Not Primary Beneficiary | Trust | Preferred Securities
Variable Interest Entity [Line Items]
Issuance of securities			35,000,000
Variable Interest Entity, Not Primary Beneficiary | Trust | Common Securities
Variable Interest Entity [Line Items]
Issuance of securities			$ 1,083,000
Number of securities issued (in securities) | Security			1,083
Operating Partnership | Variable Interest Entity, Not Primary Beneficiary | Trust III
Variable Interest Entity [Line Items]
Interest rate, fixed (as a percent)						6.91%
Interest rate swap, fixed rate of interest								4.99%
Operating Partnership | Variable Interest Entity, Not Primary Beneficiary | Trust III | LIBOR
Variable Interest Entity [Line Items]
Margin added to variable rate (as a percent)				2.40%
Operating Partnership | Variable Interest Entity, Not Primary Beneficiary | Trust II
Variable Interest Entity [Line Items]
Interest rate, fixed (as a percent)					6.67%
Interest rate swap, fixed rate of interest				4.99%
Prepayment premium				$ 0
Operating Partnership | Variable Interest Entity, Not Primary Beneficiary | Trust II | LIBOR
Variable Interest Entity [Line Items]
Margin added to variable rate (as a percent)				2.40%
Operating Partnership | Variable Interest Entity, Not Primary Beneficiary | Trust
Variable Interest Entity [Line Items]
Interest rate swap, fixed rate of interest				5.14%
Prepayment premium				$ 0
Operating Partnership | Variable Interest Entity, Not Primary Beneficiary | Trust | LIBOR
Variable Interest Entity [Line Items]
Margin added to variable rate (as a percent)				2.30%