Loans Receivable - Overall Statistics for Loans Receivable Portfolio (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commitments expiration period	4 years	4 years
Floating rate loans	$ 146.9	$ 147.9
Average floor rate	1.80%	1.80%
Percentage of loans subject to yield maintenance, or other prepayment restrictions	63.00%	64.00%
Percentage of loans open to repayment by borrower without penalty	37.00%	36.00%
USD LIBOR [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of loans receivable by type	83.00%	84.00%