Related Party Transactions and Arrangements (Merger and Other Non-Routine Transactions) (Detail) (Affiliated Entity [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	$ 65,452	$ 20,032	$ 332,923	$ 348,086
Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		750	27,265	750
Merger Related Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				125
Merger Related Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		348	72	937
Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			78,244	98,360
Furniture, Fixtures And Equipment [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			15,800	5,800
Other Non-Routine Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				61
Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		1,200	11,352	3,200
Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		2,298	137,778	109,233
Merger Related Costs Other Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			2,900
Other Non-Routine Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			2,145
ARCT III Merger [Member] | Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				0
ARCT III Merger [Member] | Merger Related Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				125
ARCT III Merger [Member] | Merger Related Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				522
ARCT III Merger [Member] | Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				98,360
ARCT III Merger [Member] | Furniture, Fixtures And Equipment [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				5,800
ARCT III Merger [Member] | Other Non-Routine Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				61
ARCT III Merger [Member] | Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				2,000
ARCT III Merger [Member] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				106,868
ARCT IV Merger [Member] | Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		750	8,400	750
ARCT IV Merger [Member] | Merger Related Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				0
ARCT IV Merger [Member] | Merger Related Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		180	0	203
ARCT IV Merger [Member] | Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			78,244	0
ARCT IV Merger [Member] | Furniture, Fixtures And Equipment [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			5,800	0
ARCT IV Merger [Member] | Other Non-Routine Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				0
ARCT IV Merger [Member] | Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		1,200	1,352	1,200
ARCT IV Merger [Member] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		2,130	94,213	2,153
ARCT IV Merger [Member] | Merger Related Costs Other Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
ARCT IV Merger [Member] | Other Non-Routine Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			417
Cole Merger [Member] | Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		0	17,115	0
Cole Merger [Member] | Merger Related Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				0
Cole Merger [Member] | Merger Related Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		85	72	85
Cole Merger [Member] | Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0	0
Cole Merger [Member] | Furniture, Fixtures And Equipment [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0	0
Cole Merger [Member] | Other Non-Routine Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				0
Cole Merger [Member] | Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		0	0	0
Cole Merger [Member] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		85	21,815	85
Cole Merger [Member] | Merger Related Costs Other Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			2,900
Cole Merger [Member] | Other Non-Routine Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			1,728
Other Acquisitions [Member] | Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		0		0
Other Acquisitions [Member] | Merger Related Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				0
Other Acquisitions [Member] | Merger Related Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		83		127
Other Acquisitions [Member] | Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				0
Other Acquisitions [Member] | Furniture, Fixtures And Equipment [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				0
Other Acquisitions [Member] | Other Non-Routine Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				0
Other Acquisitions [Member] | Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		0		0
Other Acquisitions [Member] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		83		127
Internalization And Other [Member] | Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Internalization And Other [Member] | Merger Related Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Internalization And Other [Member] | Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Internalization And Other [Member] | Furniture, Fixtures And Equipment [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			10,000
Internalization And Other [Member] | Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			10,000
Internalization And Other [Member] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			20,000
Internalization And Other [Member] | Merger Related Costs Other Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Internalization And Other [Member] | Other Non-Routine Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Multi-tenant Spin off [Member] | Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			1,750
Multi-tenant Spin off [Member] | Merger Related Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Multi-tenant Spin off [Member] | Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Multi-tenant Spin off [Member] | Furniture, Fixtures And Equipment [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Multi-tenant Spin off [Member] | Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Multi-tenant Spin off [Member] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			1,750
Multi-tenant Spin off [Member] | Merger Related Costs Other Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Multi-tenant Spin off [Member] | Other Non-Routine Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			$ 0