Loans Considered to be Impaired (Detail) - USD ($) $ in Thousands	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Financing Receivable Impaired [Line Items]
Allowance for loan losses	$ 17,097		$ 9,218		$ 22,955	$ 30,400
Commercial mortgages
Financing Receivable Impaired [Line Items]
Allowance for loan losses	3,154
Mezzanine Loans
Financing Receivable Impaired [Line Items]
Allowance for loan losses	12,139		7,892		21,636
Preferred Equity Interests
Financing Receivable Impaired [Line Items]
Allowance for loan losses	1,804		1,326		$ 1,319
Watchlist
Financing Receivable Impaired [Line Items]
Watchlist/Impaired loans expecting full recovery	77,800		67,839
Watchlist/Impaired loans with reserves	54,437		13,281
Total Watchlist/Impaired Loans	132,237	[1]	81,120	[2]
Watchlist | Commercial mortgages
Financing Receivable Impaired [Line Items]
Watchlist/Impaired loans expecting full recovery	74,800		22,920
Watchlist/Impaired loans with reserves	15,645
Total Watchlist/Impaired Loans	90,445	[1]	22,920	[2]
Watchlist | Mezzanine Loans
Financing Receivable Impaired [Line Items]
Watchlist/Impaired loans expecting full recovery	3,000		40,559
Watchlist/Impaired loans with reserves	30,846		9,631
Total Watchlist/Impaired Loans	33,846	[1]	50,190	[2]
Watchlist | Preferred Equity Interests
Financing Receivable Impaired [Line Items]
Watchlist/Impaired loans expecting full recovery			4,360
Watchlist/Impaired loans with reserves	7,946		3,650
Total Watchlist/Impaired Loans	$ 7,946	[1]	$ 8,010	[2]

[1] As of December 31, 2015, this includes no unpaid principal relating to previously identified TDRs that are on accrual status.

[2] As of December 31, 2014, this includes $5,500 of unpaid principal relating to previously identified TDRs that are on accrual status.