Derivatives - Offsetting of Derivatives Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Offsetting Assets [Line Items]
Gross Amounts, derivative assets	$ 4,448	$ 542,421
Gross Amounts Offset, derivative assets	(2,580)	(540,442)
Net Amounts Presented in the Statements of Financial Condition, derivative assets	1,868	1,979
Gross Amounts, derivative liabilities	6,733	631,571
Gross Amounts Offset, derivative liabilities	(2,580)	(540,442)
Net Amounts Presented in the Statements of Financial Condition, derivative liabilities	4,153	91,129
FX/Commodities Options [Member]
Offsetting Assets [Line Items]
Gross Amounts, derivative assets	26	482,751
Gross Amounts Offset, derivative assets		(482,712)
Net Amounts Presented in the Statements of Financial Condition, derivative assets	26	39
Gross Amounts, derivative liabilities		570,728
Gross Amounts Offset, derivative liabilities		(482,712)
Net Amounts Presented in the Statements of Financial Condition, derivative liabilities		88,016
FX Swaps [Member]
Offsetting Assets [Line Items]
Gross Amounts, derivative assets	1,672	1,938
Gross Amounts Offset, derivative assets	(394)	(327)
Net Amounts Presented in the Statements of Financial Condition, derivative assets	1,278	1,611
Gross Amounts, derivative liabilities	2,638	2,399
Gross Amounts Offset, derivative liabilities	(394)	(327)
Net Amounts Presented in the Statements of Financial Condition, derivative liabilities	2,244	2,072
Forwards [Member]
Offsetting Assets [Line Items]
Gross Amounts, derivative assets	706	253
Gross Amounts Offset, derivative assets	(142)	(17)
Net Amounts Presented in the Statements of Financial Condition, derivative assets	564	236
Gross Amounts, derivative liabilities	1,427	656
Gross Amounts Offset, derivative liabilities	(142)	(17)
Net Amounts Presented in the Statements of Financial Condition, derivative liabilities	1,285	639
Futures [Member]
Offsetting Assets [Line Items]
Gross Amounts, derivative assets	2,044	57,479
Gross Amounts Offset, derivative assets	(2,044)	(57,386)
Net Amounts Presented in the Statements of Financial Condition, derivative assets		93
Gross Amounts, derivative liabilities	2,668	57,788
Gross Amounts Offset, derivative liabilities	(2,044)	(57,386)
Net Amounts Presented in the Statements of Financial Condition, derivative liabilities	$ 624	$ 402