Derivatives - Fair Values of Derivatives Reported on Consolidated Statements of Financial Condition (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Gross derivative liability	$ 170,388	$ 193,574	$ 207,306
Total Return Swaps [Member]
Derivatives, Fair Value [Line Items]
Gross derivative assets	357	460
Gross derivative liability	9,400	958
Cash collateral pledged for total return swaps	$ 16,996	$ 9,636