Derivative Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Notional amount	$ 660,000,000				$ 761,500,000					$ 660,000,000	$ 761,500,000
Reclassified interest income (expense)	109,917,000	$ 107,803,000	$ 99,340,000	$ 85,643,000	85,922,000	$ 97,104,000	$ 92,097,000	$ 90,993,000		402,703,000	366,116,000	$ 366,370,000
Scenario, Forecast [Member] | Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Income [Member]
Derivative [Line Items]
Reclassified interest income (expense)									$ 300,000
Scenario, Forecast [Member] | Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Expense [Member]
Derivative [Line Items]
Reclassified interest income (expense)									$ (6,100,000)
Fixed Interest Swap [Member]
Derivative [Line Items]
Notional amount	35,000,000				36,500,000					35,000,000	36,500,000
Variable Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount	625,000,000				675,000,000					625,000,000	675,000,000
Receive Fixed Pay Floating Interest Rate Swaps [Member]
Derivative [Line Items]
Notional amount	0				50,000,000					0	50,000,000
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional amount	40,300,000				30,400,000					40,300,000	30,400,000
Forward Commitments [Member]
Derivative [Line Items]
Notional amount	86,100,000				33,300,000					86,100,000	33,300,000
Customer Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	582,700,000				428,400,000					582,700,000	428,400,000
Offsetting Counter Party Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	$ 582,700,000				$ 428,400,000					$ 582,700,000	$ 428,400,000