Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Certain Financial Instruments (Details) - USD ($) $ in Thousands		Mar. 31, 2026		Dec. 31, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		$ 214,120		$ 181,103
Interest-earning deposits in financial institutions		2,003,149		2,126,862
Securities available-for-sale, at fair value, net of allowance for credit losses (amortized cost of $2,857,903 and $2,646,414, respectively)		2,656,332	[1]	2,454,058	[2]
Securities available-for-sale, Carrying Amount		2,656,332
Securities held-to-maturity, at amortized cost, net of allowance for credit losses (fair value of $2,227,000 and $2,246,526, respectively)(ACL of $695 and $695, respectively)		2,313,548	[3]	2,308,636	[4]
Securities held to maturity, fair value		2,227,000	[3]	2,246,526	[4]
Investment in FHLB stock, Carrying Amount		170,342		160,442
Investment in FHLB stock, Fair Value		170,342		160,442
Loans HFS		259,049		182,936
Loans Held-for-sale, Fair Value Disclosure		259,429		183,083
Loans and leases, net	[5]	24,538,747		24,787,067
Loans Receivable HFI, Fair Value Disclosure		23,526,921		23,871,794
Equity Securities, FV-NI		1,082		2
Servicing Asset		16,968		17,480
Servicing Rights		18,653		19,427
Demand, interest checking, money market, and savings deposits		22,610,386		23,156,094
Time Deposits		4,711,748		4,687,263
Deposits, Fair Value Disclosure		4,699,767		4,684,099
Borrowings (including $111,250 and $113,634 at fair value, respectively)		2,551,250		2,063,819
Long-Term Debt, Fair Value		2,552,604		2,069,076
Subordinated debt		954,072		952,740
Subordinated Debt Obligations, Fair Value Disclosure		934,399		934,819
Derivative Liability		4,461		4,156
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		214,120		181,103
Interest-earning deposits in financial institutions		2,003,149		2,126,862
Investment in FHLB stock, Fair Value		0		0
Loans Held-for-sale, Fair Value Disclosure		0		0
Demand, interest checking, money market, and savings deposits		0		0
Deposits, Fair Value Disclosure		0		0
Long-Term Debt, Fair Value		440,000		275,185
Subordinated Debt Obligations, Fair Value Disclosure		0		0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		0		0
Interest-earning deposits in financial institutions		0		0
Investment in FHLB stock, Fair Value		170,342		160,442
Loans Held-for-sale, Fair Value Disclosure		259,429		183,083
Demand, interest checking, money market, and savings deposits		22,610,386		23,156,094
Deposits, Fair Value Disclosure		4,699,767		4,684,099
Long-Term Debt, Fair Value		2,001,354		1,680,257
Subordinated Debt Obligations, Fair Value Disclosure		934,399		934,819
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		0		0
Interest-earning deposits in financial institutions		0		0
Investment in FHLB stock, Fair Value		0		0
Loans Held-for-sale, Fair Value Disclosure		0		0
Loans Receivable HFI, Fair Value Disclosure		23,502,792		23,823,393
Warrants Not Settleable in Cash, Fair Value Disclosure				3,437
Demand, interest checking, money market, and savings deposits		0		0
Deposits, Fair Value Disclosure		0		0
Long-Term Debt, Fair Value		111,250		113,634
Subordinated Debt Obligations, Fair Value Disclosure		0		0
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value, net of allowance for credit losses (amortized cost of $2,857,903 and $2,646,414, respectively)		2,656,332		2,454,058
Warrants Not Settleable in Cash, Fair Value Disclosure		3,363	[6]	3,437
Cash flow hedges in Cash, Fair Value Disclosure, Financial Asset		5,818
Other derivative assets, Fair Value		4,362	[6]	4,124
Cash flow hedges in Cash, Fair Value Disclosure, Liabilities		1,838		4,065
Derivative Liability, Fair Value of Collateral		4,461		4,156
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value, net of allowance for credit losses (amortized cost of $2,857,903 and $2,646,414, respectively)		0		0
Securities held to maturity, fair value		184,111		185,088
Equity Securities, FV-NI		1,082		2
Warrants Not Settleable in Cash, Fair Value Disclosure		0		0
Cash flow hedges in Cash, Fair Value Disclosure, Financial Asset		0
Other derivative assets, Fair Value		0		0
Servicing Rights		0		0
Cash flow hedges in Cash, Fair Value Disclosure, Liabilities		0		0
Derivative Liability, Fair Value of Collateral		0		0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value, net of allowance for credit losses (amortized cost of $2,857,903 and $2,646,414, respectively)		2,654,082		2,451,688
Securities held to maturity, fair value		2,038,915		2,057,189
Equity Securities, FV-NI		0		0
Warrants Not Settleable in Cash, Fair Value Disclosure		0		0
Cash flow hedges in Cash, Fair Value Disclosure, Financial Asset		5,818
Other derivative assets, Fair Value		4,362		4,124
Servicing Rights		0		0
Cash flow hedges in Cash, Fair Value Disclosure, Liabilities		1,838		4,065
Derivative Liability, Fair Value of Collateral		4,461		4,156
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value, net of allowance for credit losses (amortized cost of $2,857,903 and $2,646,414, respectively)		2,250		2,370
Securities held to maturity, fair value		3,974		4,249
Equity Securities, FV-NI		0		0
Warrants Not Settleable in Cash, Fair Value Disclosure		3,363		3,437
Cash flow hedges in Cash, Fair Value Disclosure, Financial Asset		0
Other derivative assets, Fair Value		0		0
Servicing Rights		18,653		19,427
Cash flow hedges in Cash, Fair Value Disclosure, Liabilities		0		0
Derivative Liability, Fair Value of Collateral		0		0
NonPCI and PCI Loans | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable HFI, Fair Value Disclosure		0		0
NonPCI and PCI Loans | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable HFI, Fair Value Disclosure		$ 24,129		$ 48,401

[1] Excludes accrued interest receivable of $12.3 million at March 31, 2026 which is recorded in "Other assets" on the consolidated balance sheets.

[2] Excludes accrued interest receivable of $11.4 million at December 31, 2025 which is recorded in "Other assets" on the consolidated balance sheets.

[3] Excludes accrued interest receivable of $11.2 million at March 31, 2026 which is recorded in "Other assets" on the consolidated balance sheet

[4] Excludes accrued interest receivable of $13.4 million at December 31, 2025 which is recorded in "Other assets" on the consolidated balance sheets

[5] Excludes accrued interest receivable of $106.2 million and $104.3 million at March 31, 2026 and December 31, 2025, respectively, which is recorded in "Other assets" on the consolidated balance sheets.

[6] For information regarding derivative instruments, see "Note 9. Derivatives".