Fair Value of Financial Assets and Liabilities - Offsetting of Derivative Instruments and Collateralized Transactions (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross Amounts, Assets	$ 3,538	$ 3,973
Gross Amounts Offset, Assets	(326)	(546)
Net Amounts Presented in the Statements of Financial Condition, Assets	3,212	3,427
Gross Amounts Not Offset, Financial Instruments, Assets	0	0
Gross Amounts Not Offset, Cash Collateral Received, Assets	0	0
Net Amount, Assets	3,212	3,427
Gross Amounts, Liabilities	7,677	2,112
Gross Amounts Offset, Liabilities	(326)	(546)
Net Amounts Presented in the Statements of Financial Condition, Liabilities	7,351	1,566
Gross Amounts Not Offset, Financial Instruments, Liabilities	0	0
Gross Amounts Not Offset, Cash Collateral Received, Liabilities	0	0
Net Amount, Liabilities	7,351	1,566
Foreign Exchange Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross Amounts, Assets	3,141	3,441
Gross Amounts Offset, Assets	(325)	(495)
Net Amounts Presented in the Statements of Financial Condition, Assets	2,816	2,946
Gross Amounts Not Offset, Financial Instruments, Assets	0	0
Gross Amounts Not Offset, Cash Collateral Received, Assets	0	0
Net Amount, Assets	2,816	2,946
Gross Amounts, Liabilities	4,289	1,472
Gross Amounts Offset, Liabilities	(325)	(495)
Net Amounts Presented in the Statements of Financial Condition, Liabilities	3,964	977
Gross Amounts Not Offset, Financial Instruments, Liabilities	0	0
Gross Amounts Not Offset, Cash Collateral Received, Liabilities	0	0
Net Amount, Liabilities	3,964	977
Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross Amounts, Assets	227	231
Gross Amounts Offset, Assets	0	(29)
Net Amounts Presented in the Statements of Financial Condition, Assets	227	202
Gross Amounts Not Offset, Financial Instruments, Assets	0	0
Gross Amounts Not Offset, Cash Collateral Received, Assets	0	0
Net Amount, Assets	227	202
Gross Amounts, Liabilities		29
Gross Amounts Offset, Liabilities		(29)
Net Amounts Presented in the Statements of Financial Condition, Liabilities		0
Gross Amounts Not Offset, Financial Instruments, Liabilities		0
Gross Amounts Not Offset, Cash Collateral Received, Liabilities		0
Net Amount, Liabilities		0
Foreign Exchange/Commodities Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross Amounts, Assets		244
Gross Amounts Offset, Assets		0
Net Amounts Presented in the Statements of Financial Condition, Assets		244
Gross Amounts Not Offset, Financial Instruments, Assets		0
Gross Amounts Not Offset, Cash Collateral Received, Assets		0
Net Amount, Assets		244
Gross Amounts, Liabilities	1,588	41
Gross Amounts Offset, Liabilities	0	0
Net Amounts Presented in the Statements of Financial Condition, Liabilities	1,588	41
Gross Amounts Not Offset, Financial Instruments, Liabilities	0	0
Gross Amounts Not Offset, Cash Collateral Received, Liabilities	0	0
Net Amount, Liabilities	1,588	41
Forwards [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross Amounts, Assets	170	57
Gross Amounts Offset, Assets	(1)	(22)
Net Amounts Presented in the Statements of Financial Condition, Assets	169	35
Gross Amounts Not Offset, Financial Instruments, Assets	0	0
Gross Amounts Not Offset, Cash Collateral Received, Assets	0	0
Net Amount, Assets	169	35
Gross Amounts, Liabilities	66	58
Gross Amounts Offset, Liabilities	(1)	(22)
Net Amounts Presented in the Statements of Financial Condition, Liabilities	65	36
Gross Amounts Not Offset, Financial Instruments, Liabilities	0	0
Gross Amounts Not Offset, Cash Collateral Received, Liabilities	0	0
Net Amount, Liabilities	65	36
Futures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross Amounts, Liabilities	1,734	512
Gross Amounts Offset, Liabilities	0	0
Net Amounts Presented in the Statements of Financial Condition, Liabilities	1,734	512
Gross Amounts Not Offset, Financial Instruments, Liabilities	0	0
Gross Amounts Not Offset, Cash Collateral Received, Liabilities	0	0
Net Amount, Liabilities	$ 1,734	$ 512