Investment Securities (Summary Of Debt Securities Available-for-Sale) (Detail) $ in Thousands	Mar. 31, 2022 USD ($) holding	Dec. 31, 2021 USD ($) holding
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	$ 9,073,338	$ 4,227,697
Unrealized Gains	4,861	41,499
Unrealized Losses	(333,302)	(34,342)
Investment securities available-for-sale, at fair value	8,744,897	4,234,854
Less than 12 months, fair value	7,637,928	2,272,641
Less than 12 months, unrealized losses	(280,183)	(17,086)
12 months or more, fair value	692,922	558,515
12 months or more, unrealized losses	$ (53,119)	$ (17,256)
Total, number of holdings | holding	1,271	162
Total, fair value	$ 8,330,850	$ 2,831,156
Total, unrealized losses	(333,302)	(34,342)
Amortized Cost
Due in one year or less	33,293
Due after one year through five years	1,346,552
Due after five through ten years	1,522,072
Due after ten years	6,171,421
Amortized Cost - Total available-for-sale debt securities	9,073,338	4,227,697
Fair Value
Due in one year or less	33,216
Due after one year through five years	1,311,044
Due after five through ten years	1,474,896
Due after ten years	5,925,741
Fair Value, Total available-for-sale debt securities	8,744,897	4,234,854
Available-for-sale securities pledged	4,663,923	1,780,164
U.S. Treasury notes
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	754,313	398,664
Unrealized Gains	0	0
Unrealized Losses	(21,888)	(1,698)
Investment securities available-for-sale, at fair value	732,425	396,966
Less than 12 months, fair value	732,424	396,966
Less than 12 months, unrealized losses	$ (21,888)	$ (1,698)
Total, number of holdings | holding	23	8
Total, fair value	$ 732,424	$ 396,966
Total, unrealized losses	(21,888)	(1,698)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	754,313	398,664
Fair Value
Fair Value, Total available-for-sale debt securities	732,425	396,966
Government agency debentures
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	227,161
Unrealized Gains	84
Unrealized Losses	(10,026)
Investment securities available-for-sale, at fair value	217,219
Less than 12 months, fair value	194,636
Less than 12 months, unrealized losses	$ (10,026)
Total, number of holdings | holding	13
Total, fair value	$ 194,636
Total, unrealized losses	(10,026)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	227,161
Fair Value
Fair Value, Total available-for-sale debt securities	217,219
Municipal bonds and notes
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	1,946,946
Unrealized Gains	6
Unrealized Losses	(52,415)
Investment securities available-for-sale, at fair value	1,894,537
Less than 12 months, fair value	1,887,526
Less than 12 months, unrealized losses	$ (52,415)
Total, number of holdings | holding	533
Total, fair value	$ 1,887,526
Total, unrealized losses	(52,415)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	1,946,946
Fair Value
Fair Value, Total available-for-sale debt securities	1,894,537
Agency CMO
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	80,766	88,109
Unrealized Gains	127	2,326
Unrealized Losses	(1,380)	(51)
Investment securities available-for-sale, at fair value	79,513	90,384
Less than 12 months, fair value	65,378	7,895
Less than 12 months, unrealized losses	$ (1,380)	$ (51)
Total, number of holdings | holding	26	2
Total, fair value	$ 65,378	$ 7,895
Total, unrealized losses	(1,380)	(51)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	80,766	88,109
Fair Value
Fair Value, Total available-for-sale debt securities	79,513	90,384
Agency MBS
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	2,679,206	1,568,293
Unrealized Gains	4,347	36,130
Unrealized Losses	(108,984)	(11,020)
Investment securities available-for-sale, at fair value	2,574,569	1,593,403
Less than 12 months, fair value	2,097,135	506,602
Less than 12 months, unrealized losses	(90,138)	(7,354)
12 months or more, fair value	171,877	110,687
12 months or more, unrealized losses	$ (18,846)	$ (3,666)
Total, number of holdings | holding	392	70
Total, fair value	$ 2,269,012	$ 617,289
Total, unrealized losses	(108,984)	(11,020)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	2,679,206	1,568,293
Fair Value
Fair Value, Total available-for-sale debt securities	2,574,569	1,593,403
Agency CMBS
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	1,683,526	1,248,548
Unrealized Gains	14	2,537
Unrealized Losses	(99,720)	(18,544)
Investment securities available-for-sale, at fair value	1,583,820	1,232,541
Less than 12 months, fair value	1,234,865	632,213
Less than 12 months, unrealized losses	(67,130)	(6,163)
12 months or more, fair value	348,893	335,480
12 months or more, unrealized losses	$ (32,590)	$ (12,381)
Total, number of holdings | holding	132	28
Total, fair value	$ 1,583,758	$ 967,693
Total, unrealized losses	(99,720)	(18,544)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	1,683,526	1,248,548
Fair Value
Fair Value, Total available-for-sale debt securities	1,583,820	1,232,541
CMBS
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	871,981	887,640
Unrealized Gains	265	506
Unrealized Losses	(8,089)	(1,883)
Investment securities available-for-sale, at fair value	864,157	886,263
Less than 12 months, fair value	665,550	724,762
Less than 12 months, unrealized losses	(7,265)	(1,744)
12 months or more, fair value	148,459	81,253
12 months or more, unrealized losses	$ (824)	$ (139)
Total, number of holdings | holding	45	50
Total, fair value	$ 814,009	$ 806,015
Total, unrealized losses	(8,089)	(1,883)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	871,981	887,640
Fair Value
Fair Value, Total available-for-sale debt securities	864,157	886,263
CLO
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	14,245	21,860
Unrealized Gains	0	0
Unrealized Losses	(12)	(13)
Investment securities available-for-sale, at fair value	14,233	21,847
12 months or more, fair value	14,233	21,848
12 months or more, unrealized losses	$ (12)	$ (13)
Total, number of holdings | holding	1	1
Total, fair value	$ 14,233	$ 21,848
Total, unrealized losses	(12)	(13)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	14,245	21,860
Fair Value
Fair Value, Total available-for-sale debt securities	14,233	21,847
Corporate debt
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	797,694	14,583
Unrealized Gains	18	0
Unrealized Losses	(30,668)	(1,133)
Investment securities available-for-sale, at fair value	767,044	13,450
Less than 12 months, fair value	753,284	4,203
Less than 12 months, unrealized losses	(29,821)	(76)
12 months or more, fair value	9,460	9,247
12 months or more, unrealized losses	$ (847)	$ (1,057)
Total, number of holdings | holding	104	3
Total, fair value	$ 762,744	$ 13,450
Total, unrealized losses	(30,668)	(1,133)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	797,694	14,583
Fair Value
Fair Value, Total available-for-sale debt securities	767,044	13,450
Other
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	17,500
Unrealized Gains	0
Unrealized Losses	(120)
Investment securities available-for-sale, at fair value	17,380
Less than 12 months, fair value	7,130
Less than 12 months, unrealized losses	$ (120)
Total, number of holdings | holding	2
Total, fair value	$ 7,130
Total, unrealized losses	(120)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	17,500
Fair Value
Fair Value, Total available-for-sale debt securities	17,380
Pledged For Borrowings
Fair Value
Available-for-sale securities pledged	902,581	924,841
Pledged For Municipal Deposits
Fair Value
Available-for-sale securities pledged	$ 3,761,342	$ 855,323