Related Party Transactions and Arrangements (Merger and Other Non-Routine Transactions) (Detail) (Affiliated Entity [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	$ 43,809	$ 53,221	$ 267,471	$ 328,054
Merger Related Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	40	255	72	589
Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			27,265
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 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	2,000
Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			11,352
Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			137,778	106,935
Merger Related Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				125
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 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	0	23	0	23
ARCT IV Merger [Member] | Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			8,400
ARCT IV Merger [Member] | Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			78,244
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
ARCT IV Merger [Member] | Other Non Routine 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
ARCT IV Merger [Member] | Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			1,352
ARCT IV Merger [Member] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			94,213	23
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		0
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] | 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] | Other Non Routine 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
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
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	40		72
Cole Merger [Member] | Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			17,115
Cole Merger [Member] | Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Cole Merger [Member] | Furniture, Fixtures And Equipment [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Cole Merger [Member] | Other Non Routine 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
Cole Merger [Member] | Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			0
Cole Merger [Member] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party			21,815
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			2,900
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		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] | 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] | Other Non Routine 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
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
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		188		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, Personnel Costs And Other Reimbursements [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 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] | Other Non-Routine Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				61
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		44		44
Other Acquisitions [Member] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party				$ 44