Investment Securities (Summary Of Debt Securities Available-for-Sale) (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) holding	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($) holding
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	$ 9,359,626		$ 9,668,422
Unrealized Gains	32,166		50,673
Unrealized Losses	(790,651)		(759,366)
Investment securities available-for-sale, at fair value	8,601,141		8,959,729
Less than 12 months, fair value	662,633		567,445
Less than 12 months, unrealized losses	(17,189)		(17,416)
12 months or more, fair value	6,113,467		6,499,763
12 months or more, unrealized losses	$ (773,462)		$ (741,950)
Total, number of holdings | holding	1,145		1,181
Total, fair value	$ 6,776,100		$ 7,067,208
Total, unrealized losses	(790,651)		(759,366)
Amortized Cost
Maturing within 1 year	32,356
After 1 year through 5 years	597,123
After 5 through 10 years	1,271,850
After 10 years	7,458,297
Amortized Cost - Total available-for-sale debt securities	9,359,626		9,668,422
Fair Value
Maturing within 1 year	31,621
After 1 year through 5 years	565,463
After 5 through 10 years	1,173,728
After 10 years	6,830,329
Fair Value, Total available-for-sale debt securities	8,601,141		8,959,729
Available-for-sale securities pledged	8,105,862		8,213,545
Debt Securities, Available-for-sale, Realized Gain	2,240	$ 0
Debt Securities, Available-for-Sale, Realized Loss	(14,636)	$ (20,483)
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, fair value	662,633		567,445
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	17,189		17,416
12 months or more, fair value	6,113,467		6,499,763
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 773,462		$ 741,950
Total, number of holdings | holding	1,145		1,181
Total, fair value	$ 6,776,100		$ 7,067,208
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	790,651		759,366
Government agency debentures
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	302,261		302,212
Unrealized Gains	0		0
Unrealized Losses	(39,773)		(37,579)
Investment securities available-for-sale, at fair value	262,488		264,633
12 months or more, fair value	262,488		264,633
12 months or more, unrealized losses	$ (39,773)		$ (37,579)
Total, number of holdings | holding	19		19
Total, fair value	$ 262,488		$ 264,633
Total, unrealized losses	(39,773)		(37,579)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	302,261		302,212
Fair Value
Fair Value, Total available-for-sale debt securities	262,488		264,633
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
12 months or more, fair value	262,488		264,633
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 39,773		$ 37,579
Total, number of holdings | holding	19		19
Total, fair value	$ 262,488		$ 264,633
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	39,773		37,579
Municipal bonds and notes
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	1,257,643		1,626,126
Unrealized Gains	23		8
Unrealized Losses	(50,316)		(52,901)
Investment securities available-for-sale, at fair value	1,207,350		1,573,233
Less than 12 months, fair value	16,078		18,066
Less than 12 months, unrealized losses	(179)		(124)
12 months or more, fair value	1,180,389		1,536,656
12 months or more, unrealized losses	$ (50,137)		$ (52,777)
Total, number of holdings | holding	346		386
Total, fair value	$ 1,196,467		$ 1,554,722
Total, unrealized losses	(50,316)		(52,901)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	1,257,643		1,626,126
Fair Value
Fair Value, Total available-for-sale debt securities	1,207,350		1,573,233
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, fair value	16,078		18,066
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	179		124
12 months or more, fair value	1,180,389		1,536,656
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 50,137		$ 52,777
Total, number of holdings | holding	346		386
Total, fair value	$ 1,196,467		$ 1,554,722
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	50,316		52,901
Agency CMO
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	50,422		52,994
Unrealized Gains	0		0
Unrealized Losses	(4,186)		(4,053)
Investment securities available-for-sale, at fair value	46,236		48,941
12 months or more, fair value	46,236		48,941
12 months or more, unrealized losses	$ (4,186)		$ (4,053)
Total, number of holdings | holding	36		36
Total, fair value	$ 46,236		$ 48,941
Total, unrealized losses	(4,186)		(4,053)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	50,422		52,994
Fair Value
Fair Value, Total available-for-sale debt securities	46,236		48,941
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
12 months or more, fair value	46,236		48,941
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 4,186		$ 4,053
Total, number of holdings | holding	36		36
Total, fair value	$ 46,236		$ 48,941
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	4,186		4,053
Agency MBS
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	3,629,162		3,568,140
Unrealized Gains	19,414		32,461
Unrealized Losses	(284,162)		(253,503)
Investment securities available-for-sale, at fair value	3,364,414		3,347,098
Less than 12 months, fair value	187,534		71,187
Less than 12 months, unrealized losses	(892)		(272)
12 months or more, fair value	1,930,864		1,945,221
12 months or more, unrealized losses	$ (283,270)		$ (253,231)
Total, number of holdings | holding	462		457
Total, fair value	$ 2,118,398		$ 2,016,408
Total, unrealized losses	(284,162)		(253,503)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	3,629,162		3,568,140
Fair Value
Fair Value, Total available-for-sale debt securities	3,364,414		3,347,098
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, fair value	187,534		71,187
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	892		272
12 months or more, fair value	1,930,864		1,945,221
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 283,270		$ 253,231
Total, number of holdings | holding	462		457
Total, fair value	$ 2,118,398		$ 2,016,408
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	284,162		253,503
Agency CMBS
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	2,619,079		2,569,438
Unrealized Gains	12,555		18,204
Unrealized Losses	(310,404)		(299,571)
Investment securities available-for-sale, at fair value	2,321,230		2,288,071
Less than 12 months, fair value	424,108		430,070
Less than 12 months, unrealized losses	(16,031)		(16,137)
12 months or more, fair value	1,356,358		1,314,681
12 months or more, unrealized losses	$ (294,373)		$ (283,434)
Total, number of holdings | holding	148		145
Total, fair value	$ 1,780,466		$ 1,744,751
Total, unrealized losses	(310,404)		(299,571)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	2,619,079		2,569,438
Fair Value
Fair Value, Total available-for-sale debt securities	2,321,230		2,288,071
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, fair value	424,108		430,070
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	16,031		16,137
12 months or more, fair value	1,356,358		1,314,681
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 294,373		$ 283,434
Total, number of holdings | holding	148		145
Total, fair value	$ 1,780,466		$ 1,744,751
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	310,404		299,571
CMBS
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	752,086		788,478
Unrealized Gains	32		0
Unrealized Losses	(20,267)		(24,729)
Investment securities available-for-sale, at fair value	731,851		763,749
Less than 12 months, fair value	34,913		43,844
Less than 12 months, unrealized losses	(87)		(856)
12 months or more, fair value	674,009		719,905
12 months or more, unrealized losses	$ (20,180)		$ (23,873)
Total, number of holdings | holding	40		42
Total, fair value	$ 708,922		$ 763,749
Total, unrealized losses	(20,267)		(24,729)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	752,086		788,478
Fair Value
Fair Value, Total available-for-sale debt securities	731,851		763,749
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, fair value	34,913		43,844
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	87		856
12 months or more, fair value	674,009		719,905
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 20,180		$ 23,873
Total, number of holdings | holding	40		42
Total, fair value	$ 708,922		$ 763,749
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	20,267		24,729
Corporate debt
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	693,093		704,569
Unrealized Gains	142		0
Unrealized Losses	(76,026)		(82,414)
Investment securities available-for-sale, at fair value	617,209		622,155
Less than 12 months, fair value	0		4,278
Less than 12 months, unrealized losses	0		(27)
12 months or more, fair value	612,760		617,877
12 months or more, unrealized losses	$ (76,026)		$ (82,387)
Total, number of holdings | holding	89		91
Total, fair value	$ 612,760		$ 622,155
Total, unrealized losses	(76,026)		(82,414)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	693,093		704,569
Fair Value
Fair Value, Total available-for-sale debt securities	617,209		622,155
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, fair value	0		4,278
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0		27
12 months or more, fair value	612,760		617,877
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 76,026		$ 82,387
Total, number of holdings | holding	89		91
Total, fair value	$ 612,760		$ 622,155
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	76,026		82,414
Private label MBS
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	46,044		46,635
Unrealized Gains	0		0
Unrealized Losses	(4,736)		(3,827)
Investment securities available-for-sale, at fair value	41,308		42,808
Less than 12 months, fair value	0		0
Less than 12 months, unrealized losses	0		0
12 months or more, fair value	41,308		42,808
12 months or more, unrealized losses	$ (4,736)		$ (3,827)
Total, number of holdings | holding	3		3
Total, fair value	$ 41,308		$ 42,808
Total, unrealized losses	(4,736)		(3,827)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	46,044		46,635
Fair Value
Fair Value, Total available-for-sale debt securities	41,308		42,808
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, fair value	0		0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0		0
12 months or more, fair value	41,308		42,808
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 4,736		$ 3,827
Total, number of holdings | holding	3		3
Total, fair value	$ 41,308		$ 42,808
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	4,736		3,827
Other
Debt Securities, Available-for-sale [Abstract]
Amortized Cost - Total available-for-sale debt securities	9,836		9,830
Unrealized Gains	0		0
Unrealized Losses	(781)		(789)
Investment securities available-for-sale, at fair value	9,055		9,041
12 months or more, fair value	9,055		9,041
12 months or more, unrealized losses	$ (781)		$ (789)
Total, number of holdings | holding	2		2
Total, fair value	$ 9,055		$ 9,041
Total, unrealized losses	(781)		(789)
Amortized Cost
Amortized Cost - Total available-for-sale debt securities	9,836		9,830
Fair Value
Fair Value, Total available-for-sale debt securities	9,055		9,041
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
12 months or more, fair value	9,055		9,041
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 781		$ 789
Total, number of holdings | holding	2		2
Total, fair value	$ 9,055		$ 9,041
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	781		789
Pledged For Borrowings
Fair Value
Available-for-sale securities pledged	5,687,136		6,111,430
Pledged For Municipal Deposits
Fair Value
Available-for-sale securities pledged	$ 2,418,726		$ 2,102,115