Derivatives - Summary of Gains and Losses on Derivative Contracts (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain on derivative contract	$ 23,932	$ 13,223	$ 42,240	$ 21,892
Rate Lock Commitments and Forwards [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain on derivative contract	11,918	8,104	19,245	10,566
Futures [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain on derivative contract	5,740	1,749	11,648	3,698
Foreign Exchange/Commodities Options [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain on derivative contract	6,062	3,025	10,660	6,628
Foreign Exchange Swaps [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain on derivative contract	$ 212	342	590	969
Equity Options [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain on derivative contract			102
Interest Rate Swaps [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain on derivative contract		$ 3	$ (5)	$ 31