Revenues from Contracts with Customers - Schedule of Revenues from Contracts with Customers and Other Sources of Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation Of Revenue [Line Items]
Revenues	$ 357,908	$ 319,340	$ 979,307	$ 859,908
Gains from mortgage banking activities/originations, net	72,332	51,972	148,769	132,763
Servicing fees and other	52,210	45,529	137,946	117,088
Revenues	586,634	518,809	1,585,768	1,415,888
ASU No. 2014-09 [Member]
Disaggregation Of Revenue [Line Items]
Revenues	462,092	421,308	1,299,053	1,166,037
Leasing and Other Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenues	213,242	203,904	603,094	541,417
Leasing and Other Commissions [Member] | ASU No. 2014-09 [Member]
Disaggregation Of Revenue [Line Items]
Revenues	213,242	203,904	603,094	541,417
Capital Markets Commissions [Member]
Disaggregation Of Revenue [Line Items]
Revenues	144,666	115,436	376,213	318,491
Capital Markets Commissions [Member] | ASU No. 2014-09 [Member]
Disaggregation Of Revenue [Line Items]
Revenues	144,666	115,436	376,213	318,491
Management Services [Member] | ASU No. 2014-09 [Member]
Disaggregation Of Revenue [Line Items]
Revenues	$ 104,184	$ 101,968	$ 319,746	$ 306,129