Notes Payable to Trusts - Schedule of Liabilities and Maximum Exposure to Loss Related to Trusts (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Notes payable to Trusts	$ 3,240,938,000
Operating Partnership [Member]
Variable Interest Entity [Line Items]
Unamortized debt issuance costs	(9,033,000)	$ (11,698,000)
Loan Amount	610,314,000	$ 623,863,000
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investment Balance	3,590,000
Maximum exposure to loss	116,000,000
Difference	0
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Trust I [Member]
Variable Interest Entity [Line Items]
Investment Balance	1,083,000
Maximum exposure to loss	35,000,000
Difference	0
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Trust II [Member]
Variable Interest Entity [Line Items]
Investment Balance	1,269,000
Maximum exposure to loss	41,000,000
Difference	0
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Trust III [Member]
Variable Interest Entity [Line Items]
Investment Balance	1,238,000
Maximum exposure to loss	40,000,000
Difference	0
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Subtotal [Member]
Variable Interest Entity [Line Items]
Investment Balance	3,590,000
Maximum exposure to loss	116,000,000
Difference	0
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Unamortized Debt Issuance Expense [Member]
Variable Interest Entity [Line Items]
Difference	0
Trust Preferred Securities Subject to Mandatory Redemption [Member] | Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Loan Amount	117,321,000
Trust Preferred Securities Subject to Mandatory Redemption [Member] | Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Trust I [Member]
Variable Interest Entity [Line Items]
Notes payable to Trusts	36,083,000
Trust Preferred Securities Subject to Mandatory Redemption [Member] | Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Trust II [Member]
Variable Interest Entity [Line Items]
Notes payable to Trusts	42,269,000
Trust Preferred Securities Subject to Mandatory Redemption [Member] | Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Trust III [Member]
Variable Interest Entity [Line Items]
Notes payable to Trusts	41,238,000
Trust Preferred Securities Subject to Mandatory Redemption [Member] | Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Subtotal [Member]
Variable Interest Entity [Line Items]
Notes payable to Trusts	119,590,000
Trust Preferred Securities Subject to Mandatory Redemption [Member] | Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Unamortized Debt Issuance Expense [Member]
Variable Interest Entity [Line Items]
Unamortized debt issuance costs	$ (2,269,000)