Fair Values of Assets and Liabilities - Schedule of Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Financial Assets:
Interest-bearing deposits with banks	$ 3,648,117	$ 2,084,323	$ 2,448,570
Available-for-sale securities	3,912,232	3,502,915	3,611,835
Held-to-maturity securities	3,121,820	3,215,468	3,057,959
Equity securities with readily determinable fair value	125,310	139,268	134,310
FHLB and FRB stock, at cost	266,908	205,003	204,040
Brokerage customer receivables	16,662	10,592	14,042
Mortgage loans held-for-sale, at fair value	461,067	292,722	304,808
Accrued interest receivable and other	1,721,090	1,551,899	1,674,681
Financial Liabilities
FHLB advances	3,171,309	2,326,071	2,326,071
Other borrowings	647,043	645,813	643,999
Subordinated notes	298,188	437,866	437,731
Junior subordinated debentures	253,566	253,566	253,566
Carrying Value
Financial Assets:
Cash and cash equivalents	731,128	423,464	418,148
Interest-bearing deposits with banks	3,648,117	2,084,323	2,448,570
Available-for-sale securities	3,912,232	3,502,915	3,611,835
Held-to-maturity securities	3,677,420	3,856,916	3,909,150
Trading account securities	3,472	4,707	1,663
Equity securities with readily determinable fair value	125,310	139,268	134,310
FHLB and FRB stock, at cost	266,908	205,003	204,040
Brokerage customer receivables	16,662	10,592	14,042
Mortgage loans held-for-sale, at fair value	461,067	292,722	304,808
Nonqualified deferred compensation assets	16,756	15,238	14,449
Derivative assets	255,662	275,726	323,705
Accrued interest receivable and other	588,594	477,832	465,117
Total	60,770,775	53,420,537	53,295,869
Financial Liabilities
Non-maturity deposits	41,406,393	38,772,098	38,204,017
Time certificates of deposit	9,998,573	6,625,072	6,788,669
FHLB advances	3,171,309	2,326,071	2,326,071
Other borrowings	647,043	645,813	643,999
Subordinated notes	298,188	437,866	437,731
Junior subordinated debentures	253,566	253,566	253,566
Derivative liabilities	199,339	267,255	458,706
Accrued interest payable	75,254	51,116	54,383
Total financial liabilities	56,049,665	49,378,857	49,167,142
Carrying Value | Loans held-for-investment, at fair value
Financial Assets:
Loans held-for-investment	138,038	155,261	171,178
Carrying Value | Loans held-for-investment, at amortized cost
Financial Assets:
Loans held-for-investment	46,929,409	41,976,570	41,274,854
Fair Value
Financial Assets:
Cash and cash equivalents	731,128	423,464	418,148
Interest-bearing deposits with banks	3,648,117	2,084,323	2,448,570
Available-for-sale securities	3,912,232	3,502,915	3,611,835
Held-to-maturity securities	3,121,820	3,215,468	3,057,959
Trading account securities	3,472	4,707	1,663
Equity securities with readily determinable fair value	125,310	139,268	134,310
FHLB and FRB stock, at cost	266,908	205,003	204,040
Brokerage customer receivables	16,662	10,592	14,042
Mortgage loans held-for-sale, at fair value	461,067	292,722	304,808
Nonqualified deferred compensation assets	16,756	15,238	14,449
Derivative assets	255,662	275,726	323,705
Accrued interest receivable and other	588,594	477,832	465,117
Total	59,367,615	51,892,529	51,470,032
Financial Liabilities
Non-maturity deposits	41,406,393	38,772,098	38,204,017
Time certificates of deposit	9,985,778	6,603,746	6,744,989
FHLB advances	3,334,183	2,367,107	2,189,101
Other borrowings	646,272	643,755	641,514
Subordinated notes	289,260	413,501	400,520
Junior subordinated debentures	253,662	253,579	253,568
Derivative liabilities	199,339	267,255	458,706
Accrued interest payable	75,254	51,116	54,383
Total financial liabilities	56,190,141	49,372,157	48,946,798
Fair Value | Loans held-for-investment, at fair value
Financial Assets:
Loans held-for-investment	138,038	155,261	171,178
Fair Value | Loans held-for-investment, at amortized cost
Financial Assets:
Loans held-for-investment	$ 46,081,849	$ 41,090,010	$ 40,300,208