Derivative Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Notional amount	$ 810,000,000		$ 810,000,000			$ 660,000,000
Reclassified interest income (expense)	104,333,000	$ 99,340,000	210,134,000	$ 184,983,000
Increase (decrease) in derivative assets			(2,600,000)
Increase (decrease) in derivative liabilities			(5,600,000)
Scenario, Forecast [Member] | Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Income [Member]
Derivative [Line Items]
Reclassified interest income (expense)					$ 200,000
Scenario, Forecast [Member] | Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Expense [Member]
Derivative [Line Items]
Reclassified interest income (expense)					$ 4,700,000
Fixed Interest Swap [Member]
Derivative [Line Items]
Notional amount	35,000,000		35,000,000			35,000,000
Variable Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount	775,000,000		775,000,000			625,000,000
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional amount	70,600,000		70,600,000			40,300,000
Forward Commitments [Member]
Derivative [Line Items]
Notional amount	82,700,000		82,700,000			86,100,000
Customer Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	730,900,000		730,900,000			582,700,000
Offsetting Counter Party Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	730,900,000		730,900,000			$ 582,700,000
Offsetting Counter Party Derivative Instrument [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount	600,000		600,000
Foreign Currency Forward Contract [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount	$ 600,000		$ 600,000