Derivative Financial Instruments - Summary of Fair Value of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Total derivative assets	$ 16,530	$ 14,118
Total derivative liabilities	24,304	16,292
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Total derivative assets	4,931	3,351
Total derivative liabilities	3,867	5,351
Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Total derivative assets	4,931	3,351
Total derivative liabilities	3,867	5,351
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Total derivative assets	11,599	10,767
Total derivative liabilities	20,437	10,941
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Total derivative assets	10,375	10,012
Total derivative liabilities	20,400	10,933
Not Designated as Hedging Instrument [Member] | Mortgage Contracts [Member]
Derivative [Line Items]
Total derivative assets	1,141	747
Not Designated as Hedging Instrument [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Total derivative assets	83	8
Total derivative liabilities	$ 37	$ 8