Fair Values of Assets and Liabilities - Schedule of Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Financial Assets:
Interest-bearing deposits with banks	$ 2,824,314	$ 2,084,323	$ 2,163,708
Available-for-sale securities	4,329,957	3,502,915	3,492,481
Held-to-maturity securities	3,060,467	3,215,468	2,887,891
Equity securities with readily determinable fair value	112,173	139,268	116,275
FHLB and FRB stock, at cost	256,495	205,003	195,117
Brokerage customer receivables	13,682	10,592	15,722
Mortgage loans held-for-sale, at fair value	411,851	292,722	338,728
Accrued interest receivable and other	1,671,334	1,551,899	1,455,748
Financial Liabilities
FHLB advances	3,176,309	2,326,071	2,026,071
Other borrowings	606,579	645,813	665,219
Subordinated notes	298,113	437,866	437,628
Junior subordinated debentures	253,566	253,566	253,566
Carrying Value
Financial Assets:
Cash and cash equivalents	415,524	423,464	513,917
Interest-bearing deposits with banks	2,824,314	2,084,323	2,163,708
Available-for-sale securities	4,329,957	3,502,915	3,492,481
Held-to-maturity securities	3,755,924	3,856,916	3,564,473
Trading account securities	4,134	4,707	3,027
Equity securities with readily determinable fair value	112,173	139,268	116,275
FHLB and FRB stock, at cost	256,495	205,003	195,117
Brokerage customer receivables	13,682	10,592	15,722
Mortgage loans held-for-sale, at fair value	411,851	292,722	338,728
Nonqualified deferred compensation assets	16,041	15,238	14,796
Derivative assets	243,860	275,726	294,748
Accrued interest receivable and other	505,504	477,832	434,553
Total	57,564,990	53,420,537	52,170,953
Financial Liabilities
Non-maturity deposits	38,778,256	38,772,098	37,682,437
Time certificates of deposit	9,270,770	6,625,072	6,356,270
FHLB advances	3,176,309	2,326,071	2,026,071
Other borrowings	606,579	645,813	665,219
Subordinated notes	298,113	437,866	437,628
Junior subordinated debentures	253,566	253,566	253,566
Derivative liabilities	317,659	267,255	391,172
Accrued interest payable	66,373	51,116	45,359
Total financial liabilities	52,767,625	49,378,857	47,857,722
Carrying Value | Loans held-for-investment, at fair value
Financial Assets:
Loans held-for-investment	135,834	155,261	193,953
Carrying Value | Loans held-for-investment, at amortized cost
Financial Assets:
Loans held-for-investment	44,539,697	41,976,570	40,829,455
Fair Value
Financial Assets:
Cash and cash equivalents	415,524	423,464	513,917
Interest-bearing deposits with banks	2,824,314	2,084,323	2,163,708
Available-for-sale securities	4,329,957	3,502,915	3,492,481
Held-to-maturity securities	3,060,467	3,215,468	2,887,891
Trading account securities	4,134	4,707	3,027
Equity securities with readily determinable fair value	112,173	139,268	116,275
FHLB and FRB stock, at cost	256,495	205,003	195,117
Brokerage customer receivables	13,682	10,592	15,722
Mortgage loans held-for-sale, at fair value	411,851	292,722	338,728
Nonqualified deferred compensation assets	16,041	15,238	14,796
Derivative assets	243,860	275,726	294,748
Accrued interest receivable and other	505,504	477,832	434,553
Total	55,791,155	51,892,529	50,807,892
Financial Liabilities
Non-maturity deposits	38,778,256	38,772,098	37,682,437
Time certificates of deposit	9,248,374	6,603,746	6,300,161
FHLB advances	3,195,138	2,367,107	2,072,317
Other borrowings	605,305	643,755	662,156
Subordinated notes	273,666	413,501	405,762
Junior subordinated debentures	253,571	253,579	253,562
Derivative liabilities	317,659	267,255	391,172
Accrued interest payable	66,373	51,116	45,359
Total financial liabilities	52,738,342	49,372,157	47,812,926
Fair Value | Loans held-for-investment, at fair value
Financial Assets:
Loans held-for-investment	135,834	155,261	193,953
Fair Value | Loans held-for-investment, at amortized cost
Financial Assets:
Loans held-for-investment	$ 43,461,319	$ 41,090,010	$ 40,142,976