Segment Reporting - Summary of Total Assets by Segment (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total assets	$ 14,735,792	$ 13,237,158
Multifamily [Member]
Segment Reporting Information [Line Items]
Total assets	6,288,497	5,396,457
Industrial [Member]
Segment Reporting Information [Line Items]
Total assets	3,956,750	3,966,796
Hotel [Member]
Segment Reporting Information [Line Items]
Total assets	1,446,887	1,268,992
Retail [Member]
Segment Reporting Information [Line Items]
Total assets	135,711	136,273
Real Estate-Related Securities and Loans [Member]
Segment Reporting Information [Line Items]
Total assets	2,395,217	2,281,033
Other (Corporate) [Member]
Segment Reporting Information [Line Items]
Total assets	$ 512,730	$ 187,607