Derivatives - Summary of Gains and (Losses) on Derivative Contracts (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss), net on derivative contract	$ 4,057	$ 2,153	$ 8,916	$ 10,197
FX/Commodities Options [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss), net on derivative contract	30	114	228	226
FX Swaps [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss), net on derivative contract	46	670	371	1,894
Equity Options [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss), net on derivative contract				318
Futures [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss), net on derivative contract	3,478	3,720	8,966	12,529
Forwards [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss), net on derivative contract	$ 503	$ (2,351)	$ (649)	$ (4,770)