Derivative Financial Instruments (Narrative) (Detail)	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($) derivative_instruments	Jun. 30, 2019 USD ($) derivative_instruments	Dec. 31, 2018 derivative_instruments	Jun. 30, 2018 derivative_instruments
Derivative Instruments, Gain (Loss) [Line Items]
Amount to be reclassified from accumulated other comprehensive income to interest expense in the next twelve months		$ 1,400,000
Net derivative liability position, aggregate fair value	$ 124,500,000	124,500,000
Interest Rate Contract | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	6,700,000,000	6,700,000,000
Forward Commitments to Sell Mortgage Loans | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	990,600,000	990,600,000
Interest Rate Lock Commitments | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	631,700,000	631,700,000
Foreign Exchange Contract | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	$ 43,000,000.0	$ 43,000,000.0
Covered Call Options | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Number of derivative instruments held | derivative_instruments	0	0	0	0
Mortgage banking derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Number of derivative instruments held | derivative_instruments	0	0
Cash Flow Hedging | Cash flow hedge of variable rate deposits | Interest Rate Swap | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate derivatives held | derivative_instruments	18	18
Cash Flow Hedging | Cash flow hedge of variable rate deposits | Interest Rate Collar | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Number of derivative instruments held | derivative_instruments	1	1
Fair Value Hedging | Interest Rate Swap | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate derivatives held | derivative_instruments	16	16
Notional amount	$ 173,200,000	$ 173,200,000
Fair Value Hedging | Interest Rate Swap | Effective after March 31, 2019 | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate derivatives held | derivative_instruments	1	1
Notional amount	$ 6,900,000	$ 6,900,000
Mortgage banking revenue | Mortgage banking derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain on sale	$ 920,000