Investment Securities (Summary Of Investment Securities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 6,198,339	$ 5,568,188
Unrealized Gains	138,254	269,717
Unrealized Losses	(55,657)	(2,541)
Fair Value	6,280,936	5,835,364
Debt Securities, Held-to-maturity, Allowance for Credit Loss	214	299	$ 0
Debt Securities, Held-to-maturity, Current	6,198,125	5,567,889
Interest Receivable	50,700	57,800
Debt Securities, Available-for-sale [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	4,227,697	3,234,250
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	41,499	101,997
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	34,342	9,471
Investment securities available-for-sale, at fair value	4,234,854	3,326,776
Pledged Financial Instruments, Not Separately Reported, Debt Securities Held-to-Maturity	3,100,000	2,600,000
Pledged Financial Instruments, Not Separately Reported, Debt Securities Available-for-sale or Held-for-investment	1,800,000	1,300,000
Held-to-maturity Securities [Member]
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Interest Receivable	21,200	22,100
Available-for-sale Securities
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Interest Receivable	7,500
US Treasury and Government
Debt Securities, Available-for-sale [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	398,664
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,698
Investment securities available-for-sale, at fair value	396,966
Collateralized Mortgage Obligations [Member]
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	42,405	91,622
Unrealized Gains	655	1,785
Unrealized Losses	(25)	(241)
Fair Value	43,035	93,166
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Current	42,405	91,622
Debt Securities, Available-for-sale [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	88,109	148,711
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,326	6,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	51	98
Investment securities available-for-sale, at fair value	90,384	154,613
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	2,901,593	2,419,751
Unrealized Gains	71,444	137,863
Unrealized Losses	(11,788)	(84)
Fair Value	2,961,249	2,557,530
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Current	2,901,593	2,419,751
Debt Securities, Available-for-sale [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	1,568,293	1,389,100
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	36,130	68,598
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	11,020	289
Investment securities available-for-sale, at fair value	1,593,403	1,457,409
Agency commercial mortgage-backed securities (agency CMBS) [Member]
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	2,378,475	2,101,227
Unrealized Gains	11,202	60,484
Unrealized Losses	(43,844)	(2,213)
Fair Value	2,345,833	2,159,498
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Current	2,378,475	2,101,227
Debt Securities, Available-for-sale [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	1,248,548	1,092,430
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,537	26,317
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	18,544	1,514
Investment securities available-for-sale, at fair value	1,232,541	1,117,233
Commercial Mortgage Backed Securities [Member]
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	169,948	216,081
Unrealized Gains	3,381	9,214
Unrealized Losses	0	0
Fair Value	173,329	225,295
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt Securities, Held-to-maturity, Current	169,948	216,081
Debt Securities, Available-for-sale [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	887,640	512,759
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	506	1,082
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,883	5,823
Investment securities available-for-sale, at fair value	886,263	508,018
Collateralized loan obligations (CLO) [Member]
Debt Securities, Available-for-sale [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	21,860	76,693
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	13	310
Investment securities available-for-sale, at fair value	21,847	76,383
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	14,583	14,557
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,133	1,437
Investment securities available-for-sale, at fair value	13,450	13,120
Municipal Bonds [Member]
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	705,918	739,507
Unrealized Gains	51,572	60,371
Unrealized Losses	0	(3)
Fair Value	757,490	799,875
Debt Securities, Held-to-maturity, Allowance for Credit Loss	214	299
Debt Securities, Held-to-maturity, Current	705,704	$ 739,208
Callable [Member]
Debt Securities, Available-for-sale [Abstract]
Investment securities available-for-sale, at fair value	$ 1,600,000