Investment Securities (Summary Of Debt Securities Held-to Maturity - Contractual Maturities, Credit Quality and Other Information) (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Amortized Cost
Due in one year or less	$ 4,404
Due after one year through five years	52,822
Due after five years through ten years	325,186
Due after ten years	6,165,796
Amortized Cost	6,548,208	$ 6,198,339
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Due in one year or less	4,426
Due after one year through five years	54,317
Due after five years through ten years	316,818
Due after ten years	5,633,288
Fair Value	6,008,849	6,280,936
Held-to-maturity securities pledged	2,400,300	3,077,256
Moody's, Aaa Rating
Amortized Cost
Amortized Cost	365,789	377,374
Moody's, Aa1 Rating
Amortized Cost
Amortized Cost	5,637,532	5,442,277
Moody's, Aa2 Rating
Amortized Cost
Amortized Cost	202,666	227,106
Moody's, Aa3 Rating
Amortized Cost
Amortized Cost	199,903	104,232
Moody's, A1 Rating
Amortized Cost
Amortized Cost	101,058	35,878
Moody's, A2 Rating
Amortized Cost
Amortized Cost	27,691	8,260
Moody's, A3 Rating
Amortized Cost
Amortized Cost	0	0
Moody's, Baa2 Rating
Amortized Cost
Amortized Cost	0	95
Moody's, Not Rated
Amortized Cost
Amortized Cost	13,569	3,117
Agency CMO
Amortized Cost
Amortized Cost	32,469	42,405
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Fair Value	31,401	43,035
Agency CMO \| Moody's, Aaa Rating
Amortized Cost
Amortized Cost	0	0
Agency CMO \| Moody's, Aa1 Rating
Amortized Cost
Amortized Cost	32,469	42,405
Agency CMO \| Moody's, Aa2 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMO \| Moody's, Aa3 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMO \| Moody's, A1 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMO \| Moody's, A2 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMO \| Moody's, A3 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMO \| Moody's, Baa2 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMO \| Moody's, Not Rated
Amortized Cost
Amortized Cost	0	0
Agency MBS
Amortized Cost
Amortized Cost	2,795,607	2,901,593
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Fair Value	2,563,191	2,961,249
Agency MBS \| Moody's, Aaa Rating
Amortized Cost
Amortized Cost	0	0
Agency MBS \| Moody's, Aa1 Rating
Amortized Cost
Amortized Cost	2,795,607	2,901,593
Agency MBS \| Moody's, Aa2 Rating
Amortized Cost
Amortized Cost	0	0
Agency MBS \| Moody's, Aa3 Rating
Amortized Cost
Amortized Cost	0	0
Agency MBS \| Moody's, A1 Rating
Amortized Cost
Amortized Cost	0	0
Agency MBS \| Moody's, A2 Rating
Amortized Cost
Amortized Cost	0	0
Agency MBS \| Moody's, A3 Rating
Amortized Cost
Amortized Cost	0	0
Agency MBS \| Moody's, Baa2 Rating
Amortized Cost
Amortized Cost	0	0
Agency MBS \| Moody's, Not Rated
Amortized Cost
Amortized Cost	0	0
Agency CMBS
Amortized Cost
Amortized Cost	2,677,183	2,378,475
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Fair Value	2,413,184	2,345,833
Agency CMBS \| Moody's, Aaa Rating
Amortized Cost
Amortized Cost	0	0
Agency CMBS \| Moody's, Aa1 Rating
Amortized Cost
Amortized Cost	2,677,183	2,378,475
Agency CMBS \| Moody's, Aa2 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMBS \| Moody's, Aa3 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMBS \| Moody's, A1 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMBS \| Moody's, A2 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMBS \| Moody's, A3 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMBS \| Moody's, Baa2 Rating
Amortized Cost
Amortized Cost	0	0
Agency CMBS \| Moody's, Not Rated
Amortized Cost
Amortized Cost	0	0
Municipal bonds and notes
Amortized Cost
Amortized Cost	879,433	705,918
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Fair Value	845,397	757,490
Municipal bonds and notes \| Moody's, Aaa Rating
Amortized Cost
Amortized Cost	202,273	207,426
Municipal bonds and notes \| Moody's, Aa1 Rating
Amortized Cost
Amortized Cost	132,273	119,804
Municipal bonds and notes \| Moody's, Aa2 Rating
Amortized Cost
Amortized Cost	202,666	227,106
Municipal bonds and notes \| Moody's, Aa3 Rating
Amortized Cost
Amortized Cost	199,903	104,232
Municipal bonds and notes \| Moody's, A1 Rating
Amortized Cost
Amortized Cost	101,058	35,878
Municipal bonds and notes \| Moody's, A2 Rating
Amortized Cost
Amortized Cost	27,691	8,260
Municipal bonds and notes \| Moody's, A3 Rating
Amortized Cost
Amortized Cost	0	0
Municipal bonds and notes \| Moody's, Baa2 Rating
Amortized Cost
Amortized Cost	0	95
Municipal bonds and notes \| Moody's, Not Rated
Amortized Cost
Amortized Cost	13,569	3,117
CMBS
Amortized Cost
Amortized Cost	163,516	169,948
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Fair Value	155,676	173,329
CMBS \| Moody's, Aaa Rating
Amortized Cost
Amortized Cost	163,516	169,948
CMBS \| Moody's, Aa1 Rating
Amortized Cost
Amortized Cost	0	0
CMBS \| Moody's, Aa2 Rating
Amortized Cost
Amortized Cost	0	0
CMBS \| Moody's, Aa3 Rating
Amortized Cost
Amortized Cost	0	0
CMBS \| Moody's, A1 Rating
Amortized Cost
Amortized Cost	0	0
CMBS \| Moody's, A2 Rating
Amortized Cost
Amortized Cost	0	0
CMBS \| Moody's, A3 Rating
Amortized Cost
Amortized Cost	0	0
CMBS \| Moody's, Baa2 Rating
Amortized Cost
Amortized Cost	0	0
CMBS \| Moody's, Not Rated
Amortized Cost
Amortized Cost	0	0
Pledged For Borrowings
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Held-to-maturity securities pledged	753,593	1,243,139
Pledged For Municipal Deposits
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]
Held-to-maturity securities pledged	$ 1,646,707	$ 1,834,117

Amount excluding accrued interest, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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