Derivative Financial Instruments (Schedule Of Fair Value Of Derivative Financial Instruments) (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Derivative [Line Items]
Derivative assets	$ 253,509	$ 278,423	$ 301,368
Derivative liabilities	200,758	288,465	367,620
Interest Rate Contract
Derivative [Line Items]
Derivative assets	206,236	229,387	259,986
Derivative liabilities	196,091	275,843	329,590
Designated as Hedging Instrument
Derivative [Line Items]
Derivative assets	50,541	8,182	0
Derivative liabilities	40,730	54,235	73,397
Designated as Hedging Instrument | Interest Rate Contract | Cash Flow Hedging
Derivative [Line Items]
Derivative assets	50,420	8,182	0
Derivative liabilities	31,161	39,715	57,274
Designated as Hedging Instrument | Interest Rate Contract | Fair Value Hedging
Derivative [Line Items]
Derivative assets	121	0	0
Derivative liabilities	9,569	14,520	16,123
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative assets	202,968	270,241	301,368
Derivative liabilities	160,028	234,230	294,223
Not Designated as Hedging Instrument | Interest Rate Contract
Derivative [Line Items]
Derivative assets	155,695	221,205	259,986
Derivative liabilities	155,361	221,608	256,193
Not Designated as Hedging Instrument | Interest Rate Lock Commitments
Derivative [Line Items]
Derivative assets	44,313	48,925	39,816
Derivative liabilities	1,342	0	1,105
Not Designated as Hedging Instrument | Forward Commitments to Sell Mortgage Loans
Derivative [Line Items]
Derivative assets	2,920	0	1,514
Derivative liabilities	3,283	12,510	36,872
Not Designated as Hedging Instrument | Foreign Exchange Contract
Derivative [Line Items]
Derivative assets	40	111	52
Derivative liabilities	$ 42	$ 112	$ 53