Fair Value of Assets and Liabilities (Summary of Carrying Amounts and Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financial Assets:
Securities sold under agreements to repurchase with original maturities exceeding three months	$ 700,000
Interest-bearing deposits with banks	5,372,603	$ 4,802,527
Available-for-sale securities	2,327,793	3,055,839
Fair Value	2,900,694	593,767
Equity securities with readily determinable fair value	90,511	90,862
FHLB and FRB stock, at cost	135,378	135,588
Brokerage customer receivables	26,068	17,436
Mortgage loans held-for-sale, at fair value	817,912	1,272,090
Accrued interest receivable and other assets	1,084,115	1,351,455
Financial Liabilities:
Federal Home Loan Bank advances	1,241,071	1,228,429
Other borrowings	494,136	518,928
Subordinated notes	436,938	436,506
Junior subordinated debentures	253,566	253,566
Carrying Value
Financial Assets:
Cash and cash equivalents	411,205	322,474
Securities sold under agreements to repurchase with original maturities exceeding three months	700,000	0
Interest-bearing deposits with banks	5,372,603	4,802,527
Available-for-sale securities	2,327,793	3,055,839
Fair Value	2,942,285	579,138
Trading account securities	1,061	671
Equity securities with readily determinable fair value	90,511	90,862
FHLB and FRB stock, at cost	135,378	135,588
Brokerage customer receivables	26,068	17,436
Mortgage loans held-for-sale, at fair value	817,912	1,272,090
Nonqualified deferred compensation assets	16,240	15,398
Derivative assets	165,008	278,423
Accrued interest receivable and other assets	268,921	272,339
Total financial assets	48,064,089	42,921,858
Financial Liabilities:
Non-maturity deposits	38,126,796	32,116,023
Deposits with stated maturities	3,968,789	4,976,628
Federal Home Loan Bank advances	1,241,071	1,228,429
Other borrowings	494,136	518,928
Subordinated notes	436,938	436,506
Junior subordinated debentures	253,566	253,566
Derivative liabilities	123,000	288,465
Accrued interest payable	9,304	15,645
Total financial liabilities	44,653,600	39,834,190
Carrying Value | Loans held-for-investment, at fair value
Financial Assets:
Loans, net of unearned income	38,598	55,134
Carrying Value | Loans held-for-investment, at amortized cost
Financial Assets:
Loans, net of unearned income	34,750,506	32,023,939
Fair Value
Financial Assets:
Cash and cash equivalents	411,205	322,474
Securities sold under agreements to repurchase with original maturities exceeding three months	700,000	0
Interest-bearing deposits with banks	5,372,603	4,802,527
Available-for-sale securities	2,327,793	3,055,839
Fair Value	2,900,694	593,767
Trading account securities	1,061	671
Equity securities with readily determinable fair value	90,511	90,862
FHLB and FRB stock, at cost	135,378	135,588
Brokerage customer receivables	26,068	17,436
Mortgage loans held-for-sale, at fair value	817,912	1,272,090
Nonqualified deferred compensation assets	16,240	15,398
Derivative assets	165,008	278,423
Accrued interest receivable and other assets	268,921	272,339
Total financial assets	48,569,870	42,784,231
Financial Liabilities:
Non-maturity deposits	38,126,796	32,116,023
Deposits with stated maturities	3,965,372	4,969,849
Federal Home Loan Bank advances	1,186,280	1,172,315
Other borrowings	494,670	518,928
Subordinated notes	472,684	473,093
Junior subordinated debentures	212,226	204,713
Derivative liabilities	123,000	288,465
Accrued interest payable	9,304	15,645
Total financial liabilities	44,590,332	39,759,031
Fair Value | Loans held-for-investment, at fair value
Financial Assets:
Loans, net of unearned income	38,598	55,134
Fair Value | Loans held-for-investment, at amortized cost
Financial Assets:
Loans, net of unearned income	$ 35,297,878	$ 31,871,683