Revenues from Contracts with Customers - Schedule of Revenues from Contracts with Customers and Our Other Sources of Revenues (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers	$ 357,668
Other sources of revenue	430,460
Leasing and Other Commissions [Member]
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers	159,371
Capital Markets [Member]
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers	101,364
Management Services [Member]
Revenues From Contracts With Customers [Line Items]
Revenues from contracts with customers	96,933
Gains From Mortgage Banking Activities Originations Net [Member]
Revenues From Contracts With Customers [Line Items]
Other sources of revenue	38,914
Servicing Fees And Other [Member]
Revenues From Contracts With Customers [Line Items]
Other sources of revenue	$ 33,878