Derivative Financial Instruments (Narrative) (Detail)	6 Months Ended
	Jun. 30, 2018 USD ($) derivative_instruments	Dec. 31, 2017 derivative_instruments	Jun. 30, 2017 derivative_instruments
Derivative Instruments, Gain (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income to interest expense in the next twelve months	$ 12,500,000
Net derivative liability position, aggregate fair value	263,000
Interest Rate Contract | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	5,400,000,000
Forward Commitments to Sell Mortgage Loans | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	859,200,000
Interest Rate Lock Commitments | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	416,100,000
Foreign Exchange Contract | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	$ 39,500,000
Covered Call Options | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Number of derivative instruments held | derivative_instruments	0	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	8
Fair Value Hedging | Interest Rate Swap | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate derivatives held | derivative_instruments	13
Notional amount	$ 196,300,000.0
Outstanding balance	$ 116,991,000
Fair Value Hedging | Interest Rate Swap | Effective After June 30, 2018 | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate derivatives held | derivative_instruments	2
Notional amount	$ 69,700,000.0
Outstanding balance	$ 0