Derivatives - Offsetting of Derivative Instruments (Detail) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Offsetting Assets [Line Items]
Gross Amounts, derivative assets		$ 5,719	$ 542,421
Gross Amounts Offset, derivative assets		(1,904)	(540,442)
Net Amounts Presented in the Statements of Financial Condition, derivative assets	[1]	3,815	1,979
Gross Amounts, derivative liabilities		7,265	631,571
Gross Amounts Offset, derivative liabilities		(1,904)	(540,442)
Net Amounts Presented in the Statements of Financial Condition, derivative liabilities	[1]	5,361	91,129
Foreign Exchange/Commodities Options [Member]
Offsetting Assets [Line Items]
Gross Amounts, derivative assets		1,022	482,751
Gross Amounts Offset, derivative assets		(1,020)	(482,712)
Net Amounts Presented in the Statements of Financial Condition, derivative assets	[1]	2	39
Gross Amounts, derivative liabilities		1,091	570,728
Gross Amounts Offset, derivative liabilities		(1,020)	(482,712)
Net Amounts Presented in the Statements of Financial Condition, derivative liabilities	[1]	71	88,016
Foreign Exchange Swaps [Member]
Offsetting Assets [Line Items]
Gross Amounts, derivative assets		3,569	1,938
Gross Amounts Offset, derivative assets		(221)	(327)
Net Amounts Presented in the Statements of Financial Condition, derivative assets	[1]	3,348	1,611
Gross Amounts, derivative liabilities		2,503	2,399
Gross Amounts Offset, derivative liabilities		(221)	(327)
Net Amounts Presented in the Statements of Financial Condition, derivative liabilities	[1]	2,282	2,072
Forwards [Member]
Offsetting Assets [Line Items]
Gross Amounts, derivative assets		349	253
Gross Amounts Offset, derivative assets		(11)	(17)
Net Amounts Presented in the Statements of Financial Condition, derivative assets	[1]	338	236
Gross Amounts, derivative liabilities		2,615	656
Gross Amounts Offset, derivative liabilities		(11)	(17)
Net Amounts Presented in the Statements of Financial Condition, derivative liabilities	[1]	2,604	639
Futures [Member]
Offsetting Assets [Line Items]
Gross Amounts, derivative assets		779	57,479
Gross Amounts Offset, derivative assets		(652)	(57,386)
Net Amounts Presented in the Statements of Financial Condition, derivative assets	[1]	127	93
Gross Amounts, derivative liabilities		1,056	57,788
Gross Amounts Offset, derivative liabilities		(652)	(57,386)
Net Amounts Presented in the Statements of Financial Condition, derivative liabilities	[1]	$ 404	$ 402

[1] There were no additional balances in gross amounts not offset as of September 30, 2019 and December 31, 2018, respectively.