Derivative Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Notional amount	$ 1,482,000,000				$ 708,500,000				$ 1,482,000,000	$ 708,500,000
Percentage of periodic changes in fair value qualifies for hedge accounting treatment	100.00%								100.00%
Reclassified interest income (expense)	$ 146,225,000	$ 130,842,000	$ 131,963,000	$ 128,572,000	118,556,000	$ 108,478,000	$ 104,333,000	$ 105,801,000	$ 537,602,000	437,168,000	$ 402,703,000
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Income [Member]
Derivative [Line Items]
Reclassified interest income (expense)									1,200,000
Reclassifications out of Accumulated Other Comprehensive Income (Loss) [Member] | Interest Expense [Member]
Derivative [Line Items]
Reclassified interest income (expense)									(400,000)
Fixed Interest Swap [Member]
Derivative [Line Items]
Notional amount	757,000,000.0				33,500,000				757,000,000.0	33,500,000
Variable Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount	525,000,000.0				675,000,000.0				525,000,000.0	675,000,000.0
Variable Interest Rate Collars [Member]
Derivative [Line Items]
Notional amount	200,000,000.0								200,000,000.0
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional amount	27,600,000				29,900,000				27,600,000	29,900,000
Forward Commitments [Member]
Derivative [Line Items]
Notional amount	34,500,000				41,200,000				34,500,000	41,200,000
Customer Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	793,400,000				826,600,000				793,400,000	826,600,000
Offsetting Counter Party Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	793,400,000				826,600,000				793,400,000	826,600,000
Offsetting Counter Party Derivative Instrument [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount	3,600,000				800,000				3,600,000	800,000
Foreign Currency Forward Contract [Member] | Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount	$ 3,600,000				$ 800,000				$ 3,600,000	$ 800,000