Derivative Financial Instruments (Narrative) (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) derivative_instruments	Jun. 30, 2016 USD ($) derivative_instruments	Jun. 30, 2017 USD ($) derivative_instruments	Jun. 30, 2016 USD ($) derivative_instruments	Dec. 31, 2016 derivative_instruments
Derivative Instruments, Gain (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income to interest expense in the next twelve months			$ 2,300,000
Derivative, Net Liability Position, Aggregate Fair Value	$ 11,300,000		11,300,000
Interest Rate Contract | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	4,800,000,000		4,800,000,000
Forward Commitments to Sell Mortgage Loans | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	824,300,000		824,300,000
Interest Rate Lock Commitments | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	446,200,000		446,200,000
Foreign Exchange Contract | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	$ 39,700,000		$ 39,700,000
Covered Call Options | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Number of Instruments Held | derivative_instruments	0	0	0	0	0
Minimum | Interest Rate Contract | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, maturity date			Jul. 31, 2017
Maximum | Interest Rate Contract | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, maturity date			Feb. 28, 2045
Cash Flow Hedging | Interest Rate Contract | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net			$ 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	4		4
Cash Flow Hedging | Interest Rate Swap, $200 million, June 2019 | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	$ 200,000,000		$ 200,000,000
Cash Flow Hedging | Interest Rate Swap, $200 million, June 2019 | Interest Rate Swap | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	200,000,000		200,000,000
Cash Flow Hedging | Interest Rate Swap, $250 million, July 2019 | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	250,000,000		250,000,000
Cash Flow Hedging | Interest Rate Swap, $250 million, July 2019 | Interest Rate Swap | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	250,000,000		250,000,000
Cash Flow Hedging | Interest Rate Swap, $275 million, August 2019 | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	275,000,000		275,000,000
Cash Flow Hedging | Interest Rate Swap, $275 million, August 2019 | Interest Rate Swap | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	275,000,000		275,000,000
Cash Flow Hedging | Interest Rate Swap, $200 million, June 2020 | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	200,000,000		200,000,000
Cash Flow Hedging | Interest Rate Swap, $200 million, June 2020 | Interest Rate Swap | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	$ 200,000,000		$ 200,000,000
Cash Flow Hedging | Cash Flow Hedge of Junior Subordinated Debentures | Interest Rate Cap | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Number of Interest Rate Derivatives Held | derivative_instruments	2		2
Fair Value Hedging | Interest Rate Swap | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Number of Interest Rate Derivatives Held | derivative_instruments	11		11
Notional amount	$ 121,100,000		$ 121,100,000
Fair Value Hedging | Interest Rate Contract | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Income Statement Gain/(Loss) due to Hedge Ineffectiveness	$ 40,000	$ 17,000	$ 29,000	$ (22,000)