Debt (Summary of Outstanding and Carrying Value of Collateral by Asset Type) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Outstanding Balance	$ 6,553,066	$ 8,059,802
Other Debt [Member]
Debt Instrument [Line Items]
Collateral Carrying Value	58,025
Long-term Debt, Gross	23,010	$ 33,463
Other Debt [Member] \| Mortgage notes receivable [Member]
Debt Instrument [Line Items]
Outstanding Balance	7,279
Collateral Carrying Value	19,457
Other Debt [Member] \| Intercompany mortgage loans [Member]
Debt Instrument [Line Items]
Outstanding Balance	1,754
Collateral Carrying Value	4,212
Other Debt [Member] \| CMBS [Member]
Debt Instrument [Line Items]
Outstanding Balance	13,977
Collateral Carrying Value	$ 34,356

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant