Loans Receivable, Net - Overall Statistics for Loans Receivable Portfolio (Parenthetical) (Detail)	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of loans subject to yield maintenance, or other prepayment restrictions	63.00%	75.00%
Percentage of loans open to repayment by borrower without penalty	37.00%	25.00%
USD LIBOR [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of loans receivable by type	99.00%	98.00%
Percentage of loans, fixed rate	1.00%	2.00%