Derivative Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Derivative [Line Items]
Notional amount	$ 1,034,000,000.000		$ 1,034,000,000.000		$ 708,500,000
Percentage of periodic changes in fair value qualifies for hedge accounting treatment	100.00%		100.00%
Reclassified interest income (expense)	$ 130,842,000	$ 108,478,000	$ 391,377,000	$ 318,612,000
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Income [Member]
Derivative [Line Items]
Reclassified interest income (expense)			1,700,000
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Expense [Member]
Derivative [Line Items]
Reclassified interest income (expense)			(500,000)
Fixed Interest Swap [Member]
Derivative [Line Items]
Notional amount	408,500,000		408,500,000		33,500,000
Variable Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount	525,000,000.0		525,000,000.0		675,000,000.0
Variable Interest Rate Collar [Member]
Derivative [Line Items]
Notional amount	100,000,000.0		100,000,000.0
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional amount	39,900,000		39,900,000		29,900,000
Forward Commitments [Member]
Derivative [Line Items]
Notional amount	55,200,000		55,200,000		41,200,000
Customer Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	807,400,000		807,400,000		826,600,000
Offsetting Counter Party Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	807,400,000		807,400,000		826,600,000
Offsetting Counter Party Derivative Instrument [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount	4,500,000		4,500,000		800,000
Foreign Currency Forward Contract [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount	$ 4,500,000		$ 4,500,000		$ 800,000