Related Party Transactions and Arrangements (Revenue from Managed REITs) (Details) $ in Thousands		12 Months Ended
	Jan. 29, 2015 USD ($) property	Dec. 31, 2015 USD ($) property real_estate_program	Dec. 31, 2014 USD ($)
Related Party Transaction [Line Items]
Related-party revenues		$ 110,809	$ 202,434
Number of real estate programs excluded from related party revenues | real_estate_program		1,031
2015 Property Dispositions [Member]
Related Party Transaction [Line Items]
Number of properties sold owned by consolidated joint venture | property		2
Consolidated Joint Venture [Member] | 2015 Property Dispositions [Member]
Related Party Transaction [Line Items]
Number of properties sold owned by consolidated joint venture | property	1	1
Affiliated Entity [Member] | Revolving Credit Facility [Member] | Credit Facility [Member]
Related Party Transaction [Line Items]
Interest income		$ 1,275	307
Offering-related fees and reimbursements [Member]
Related Party Transaction [Line Items]
Related-party revenues		24,410	87,109
Securities commissions [Member]
Related Party Transaction [Line Items]
Related-party revenues		14,101	57,023
Dealer manager and distribution fees [Member]
Related Party Transaction [Line Items]
Related-party revenues		5,131	17,533
Reimbursement revenue [Member]
Related Party Transaction [Line Items]
Related-party revenues		5,178	12,553
Transaction service fees and reimbursements [Member]
Related Party Transaction [Line Items]
Related-party revenues		25,881	64,710
Acquisition fees [Member]
Related Party Transaction [Line Items]
Related-party revenues		18,742	60,426
Disposition fees [Member]
Related Party Transaction [Line Items]
Related-party revenues		4,974	0
Reimbursement revenues [Member]
Related Party Transaction [Line Items]
Related-party revenues		2,165	4,284
Management fees and reimbursements [Member]
Related Party Transaction [Line Items]
Related-party revenues		59,243	50,308
Asset and property management fees and leasing fees [Member]
Related Party Transaction [Line Items]
Related-party revenues		452	596
Advisory and performance fee revenue [Member]
Related Party Transaction [Line Items]
Related-party revenues		44,948	40,906
Reimbursement revenues [Member]
Related Party Transaction [Line Items]
Related-party revenues		$ 13,843	8,806
Selling commissions [Member]
Related Party Transaction [Line Items]
Selling commissions reallowed		100.00%
Dealer manager fees reimbursement [Member]
Related Party Transaction [Line Items]
Related-party revenues		$ 2,000	9,200
Disposition fee revenue [Member] | Consolidated Joint Venture [Member] | 2015 Property Dispositions [Member]
Related Party Transaction [Line Items]
Related-party revenues	$ 600
Disposition fee revenue [Member] | CCIT [Member]
Related Party Transaction [Line Items]
Related-party revenues	$ 4,400
Revenue from Managed Real Estate Investment Trusts, Excluding Fees from Real Estate Programs [Member]
Related Party Transaction [Line Items]
Related-party revenues		$ 5,300	$ 1,400