Related Party Transactions and Arrangements (Merger and Other Non-Routine Transactions) (Detail) (Affiliated Entity [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	$ 223,662	$ 274,833
Merger Related Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	72
Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	78,244
Furniture, Fixtures And Equipment [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	15,800
Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	11,352
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
Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	137,738
Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	27,265
Other Non-Routine Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	2,105
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		334
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] | 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] | 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] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		106,680
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
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] | 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] | 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] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	94,213
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] | 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
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] | Other Non-Routine Costs, Legal Fees And Expenses [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	0
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] | Strategic Advisory Services [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
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	72
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] | Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	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	2,900
Cole Merger [Member] | Merger And Acquisition Related Costs [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	21,775
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] | Other Non-Routine Costs, Personnel Costs And Other Reimbursements [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	1,688
MT-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
MT-Spin Off [Member] | Subordinated Distributions [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	0
MT-Spin Off [Member] | Furniture, Fixtures And Equipment [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	0
MT-Spin Off [Member] | Post Transaction Support Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	0
MT-Spin Off [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
MT-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
MT-Spin Off [Member] | Strategic Advisory Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	1,750
MT-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