Fair Values of Assets and Liabilities - Schedule of Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Financial Assets:
Interest-bearing deposits with banks	$ 2,448,570	$ 1,988,719	$ 3,968,605
Available-for-sale securities	3,611,835	3,243,017	2,923,653
Held-to-maturity securities	3,057,959	2,949,821	2,679,326
Equity securities with readily determinable fair value	134,310	110,365	114,012
FHLB and FRB stock, at cost	204,040	224,759	178,156
Brokerage customer receivables	14,042	16,387	20,327
Mortgage loans held-for-sale, at fair value	304,808	299,935	376,160
Accrued interest receivable and other	1,674,681	1,391,342	1,316,305
Financial Liabilities
FHLB advances	2,326,071	2,316,071	2,316,071
Other borrowings	643,999	596,614	447,215
Subordinated notes	437,731	437,392	437,260
Junior subordinated debentures	253,566	253,566	253,566
Carrying Value
Financial Assets:
Cash and cash equivalents	418,148	490,966	489,647
Interest-bearing deposits with banks	2,448,570	1,988,719	3,968,605
Available-for-sale securities	3,611,835	3,243,017	2,923,653
Held-to-maturity securities	3,909,150	3,640,567	3,389,842
Trading account securities	1,663	1,127	179
Equity securities with readily determinable fair value	134,310	110,365	114,012
FHLB and FRB stock, at cost	204,040	224,759	178,156
Brokerage customer receivables	14,042	16,387	20,327
Mortgage loans held-for-sale, at fair value	304,808	299,935	376,160
Nonqualified deferred compensation assets	14,449	13,899	13,387
Derivative assets	323,705	296,848	313,480
Accrued interest receivable and other	465,117	379,719	317,142
Total	53,295,869	49,902,793	50,272,203
Financial Liabilities
Non-maturity deposits	38,204,017	38,167,409	38,720,873
Deposits with stated maturities	6,788,669	4,735,135	4,076,318
FHLB advances	2,326,071	2,316,071	2,316,071
Other borrowings	643,999	596,614	447,215
Subordinated notes	437,731	437,392	437,260
Junior subordinated debentures	253,566	253,566	253,566
Derivative liabilities	458,706	338,078	357,170
Accrued interest payable	54,383	22,176	18,479
Total financial liabilities	49,167,142	46,866,441	46,626,952
Carrying Value | Loans held-for-investment, at fair value
Financial Assets:
Loans held-for-investment	171,178	179,932	156,893
Carrying Value | Loans held-for-investment, at amortized cost
Financial Assets:
Loans held-for-investment	41,274,854	39,016,553	38,010,720
Fair Value
Financial Assets:
Cash and cash equivalents	418,148	490,966	489,647
Interest-bearing deposits with banks	2,448,570	1,988,719	3,968,605
Available-for-sale securities	3,611,835	3,243,017	2,923,653
Held-to-maturity securities	3,057,959	2,949,821	2,679,326
Trading account securities	1,663	1,127	179
Equity securities with readily determinable fair value	134,310	110,365	114,012
FHLB and FRB stock, at cost	204,040	224,759	178,156
Brokerage customer receivables	14,042	16,387	20,327
Mortgage loans held-for-sale, at fair value	304,808	299,935	376,160
Nonqualified deferred compensation assets	14,449	13,899	13,387
Derivative assets	323,705	296,848	313,480
Accrued interest receivable and other	465,117	379,719	317,142
Total	51,470,032	48,214,172	48,775,720
Financial Liabilities
Non-maturity deposits	38,204,017	38,167,409	38,720,873
Deposits with stated maturities	6,744,989	4,085,058	4,087,196
FHLB advances	2,189,101	2,219,983	2,230,921
Other borrowings	641,514	569,342	447,971
Subordinated notes	400,520	409,395	417,363
Junior subordinated debentures	253,568	253,405	285,238
Derivative liabilities	458,706	338,078	357,170
Accrued interest payable	54,383	22,176	18,479
Total financial liabilities	48,946,798	46,064,846	46,565,211
Fair Value | Loans held-for-investment, at fair value
Financial Assets:
Loans held-for-investment	171,178	179,932	156,893
Fair Value | Loans held-for-investment, at amortized cost
Financial Assets:
Loans held-for-investment	$ 40,300,208	$ 38,018,678	$ 37,224,753