Derivative Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Derivative [Line Items]
Notional amount	$ 1,034,000,000		$ 1,034,000,000		$ 708,500,000
Percentage of periodic changes in fair value qualifies for hedge accounting treatment	100.00%		100.00%
Reclassified interest income (expense)	$ 131,963,000	$ 104,333,000	$ 260,535,000	$ 210,134,000
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Income [Member]
Derivative [Line Items]
Reclassified interest income (expense)			2,000,000
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Expense [Member]
Derivative [Line Items]
Reclassified interest income (expense)			800,000
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	625,000,000		625,000,000		675,000,000
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional amount	59,300,000		59,300,000		29,900,000
Forward Commitments [Member]
Derivative [Line Items]
Notional amount	76,100,000		76,100,000		41,200,000
Customer Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	827,600,000		827,600,000		826,600,000
Offsetting Counter Party Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	827,600,000		827,600,000		826,600,000
Offsetting Counter Party Derivative Instrument [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount	2,100,000		2,100,000		800,000
Foreign Currency Forward Contract [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount	$ 2,100,000		$ 2,100,000		$ 800,000