Internal CRE Debt and Preferred Equity Ratings (Detail) - Commercial Mortgage - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Real Estate [Line Items]
Percentage of Loan Portfolio		100.00%	100.00%
Performing		$ 370,829	$ 398,771
Performing Closely Monitored		428,263	413,487
Performing Special Mention		132,377	162,757
Internal Rating Substandard		0	0
Doubtful		0	0
Loss		0	0
Total	[1]	$ 931,469	$ 975,015
Mezzanine Loans
Real Estate [Line Items]
Percentage of Loan Portfolio		42.30%	46.50%
Performing		$ 195,435	$ 254,337
Performing Closely Monitored		179,188	170,039
Performing Special Mention		19,187	29,317
Internal Rating Substandard		0	0
Doubtful		0	0
Loss		0	0
Total		$ 393,810	$ 453,693
Senior Mortgages
Real Estate [Line Items]
Percentage of Loan Portfolio		56.70%	52.60%
Performing		$ 175,394	$ 144,434
Performing Closely Monitored		249,075	243,448
Performing Special Mention		104,190	124,440
Internal Rating Substandard		0	0
Doubtful		0	0
Loss		0	0
Total		$ 528,659	$ 512,322
Preferred Equity Interests
Real Estate [Line Items]
Percentage of Loan Portfolio		1.00%	0.90%
Performing Special Mention		$ 9,000	$ 9,000
Internal Rating Substandard		0	0
Doubtful		0	0
Loss		0	0
Total		$ 9,000	$ 9,000

[1] Excludes Loans held for sale, net.