Fair Value of Assets and Liabilities - Schedule of Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024
Financial Assets:
Interest-bearing deposits with banks	$ 3,422,452	$ 4,409,753	$ 3,648,117
Available-for-sale securities	5,274,124	4,141,482	3,912,232
Held-to-maturity securities	2,860,970	2,910,550	3,121,820
Equity securities with readily determinable fair value	63,445	215,412	125,310
FHLB and FRB stock, at cost	282,755	281,407	266,908
Brokerage customer receivables	0	18,102	16,662
Mortgage loans held-for-sale, at fair value	333,883	331,261	461,067
Accrued interest receivable and other	1,614,674	1,739,334	1,721,090
Financial Liabilities:
FHLB advances	3,151,309	3,151,309	3,171,309
Other borrowings	579,328	534,803	647,043
Subordinated notes	298,536	298,283	298,188
Junior subordinated debentures	253,566	253,566	253,566
Carrying Value
Financial Assets:
Cash and cash equivalents	565,469	458,536	731,128
Interest-bearing deposits with banks	3,422,452	4,409,753	3,648,117
Available-for-sale securities	5,274,124	4,141,482	3,912,232
Held-to-maturity securities	3,438,406	3,613,263	3,677,420
Trading account securities	0	4,072	3,472
Equity securities with readily determinable fair value	63,445	215,412	125,310
FHLB and FRB stock, at cost	282,755	281,407	266,908
Brokerage customer receivables	0	18,102	16,662
Mortgage loans held-for-sale, at fair value	333,883	331,261	461,067
Nonqualified deferred compensation assets	17,902	16,653	16,756
Derivative assets	208,957	200,027	255,662
Accrued interest receivable and other	587,274	563,625	588,594
Total	66,258,149	62,308,630	60,770,775
Financial Liabilities:
Non-maturity deposits	46,292,925	43,092,318	41,406,393
Deposits with stated maturities	10,418,456	9,420,031	9,998,573
FHLB advances	3,151,309	3,151,309	3,171,309
Other borrowings	579,328	534,803	647,043
Subordinated notes	298,536	298,283	298,188
Junior subordinated debentures	253,566	253,566	253,566
Derivative liabilities	141,705	241,750	199,339
Accrued interest payable	69,453	48,364	75,254
Total financial liabilities	61,205,278	57,040,424	56,049,665
Carrying Value | Loans held-for-investment, at fair value
Financial Assets:
Loans held-for-investment	129,593	158,795	138,038
Carrying Value | Loans held-for-investment, at amortized cost
Financial Assets:
Loans held-for-investment	51,933,889	47,896,242	46,929,409
Fair Value
Financial Assets:
Cash and cash equivalents	565,469	458,536	731,128
Interest-bearing deposits with banks	3,422,452	4,409,753	3,648,117
Available-for-sale securities	5,274,124	4,141,482	3,912,232
Held-to-maturity securities	2,860,970	2,910,550	3,121,820
Trading account securities	0	4,072	3,472
Equity securities with readily determinable fair value	63,445	215,412	125,310
FHLB and FRB stock, at cost	282,755	281,407	266,908
Brokerage customer receivables	0	18,102	16,662
Mortgage loans held-for-sale, at fair value	333,883	331,261	461,067
Nonqualified deferred compensation assets	17,902	16,653	16,756
Derivative assets	208,957	200,027	255,662
Accrued interest receivable and other	587,274	563,625	588,594
Total	65,002,385	60,779,924	59,367,615
Financial Liabilities:
Non-maturity deposits	46,292,925	43,092,318	41,406,393
Deposits with stated maturities	10,424,097	9,423,976	9,985,778
FHLB advances	3,185,090	3,153,524	3,334,183
Other borrowings	579,479	534,406	646,272
Subordinated notes	295,974	286,683	289,260
Junior subordinated debentures	253,591	253,588	253,662
Derivative liabilities	141,705	241,750	199,339
Accrued interest payable	69,453	48,364	75,254
Total financial liabilities	61,242,314	57,034,609	56,190,141
Fair Value | Loans held-for-investment, at fair value
Financial Assets:
Loans held-for-investment	129,593	158,795	138,038
Fair Value | Loans held-for-investment, at amortized cost
Financial Assets:
Loans held-for-investment	$ 51,255,561	$ 47,070,249	$ 46,081,849