Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Certain Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2023		Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		$ 182,261		$ 212,273
Interest-earning deposits in financial institutions		5,887,406		2,027,949
Securities available-for-sale, Carrying Amount		4,487,172		4,843,487
Investment in FHLB stock, Carrying Amount		17,250		34,290
Investment in FHLB stock, Fair Value		17,250		34,290
Loans Held-for-sale, Fair Value Disclosure		188,906		65,501
Loans Receivable Held-for-sale, Amount		188,866		65,076
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss		2,282,586	[1]	2,269,135	[2]
Loans and leases, net	[3]	21,698,649		28,408,397
Loans and leases held for investment, net		19,585,880		26,627,985
Equity Securities, FV-NI		1		1
Servicing rights		701		633
Demand, interest checking, money market, and savings deposits		19,483,888		29,198,491
Time deposits		7,114,793		4,737,843
Time deposits		7,063,958		4,700,054
Borrowings (including $123,782 at fair value)		6,294,525		1,764,030
Borrowings		6,278,804		1,764,037
Subordinated debt		870,896		867,087
Subordinated Debt Obligations, Fair Value Disclosure		729,712		870,534
Derivative Liability		6,931		5,906
Debt Securities, Held-to-maturity, Fair Value		2,013,295	[1]	2,110,472	[2]
Securities available-for-sale, at fair value (amortized cost of $5,443,677 and $5,654,617, respectively)		4,487,172		4,843,487
U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss		186,308		184,162
Debt Securities, Held-to-maturity, Fair Value		165,663		171,700
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		182,261		212,273
Interest-earning deposits in financial institutions		5,887,406		2,027,949
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
Time deposits		0		0
Borrowings		4,894,279		882,000
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		17,250		34,290
Loans Held-for-sale, Fair Value Disclosure		188,906		65,501
Demand, interest checking, money market, and savings deposits		19,483,888		29,198,491
Time deposits		7,063,958		4,700,054
Borrowings		0		750,007
Subordinated Debt Obligations, Fair Value Disclosure		729,712		870,534
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 and leases held for investment, net		19,557,646		26,599,920
Equity warrants				4,048
Demand, interest checking, money market, and savings deposits		0		0
Time deposits		0		0
Borrowings		1,384,525		132,030
Subordinated Debt Obligations, Fair Value Disclosure		0		0
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity warrants		3,807		4,048
Other derivative assets, Fair Value		8,463		7,814
Derivative liabilities		6,931		5,906
Securities available-for-sale, at fair value (amortized cost of $5,443,677 and $5,654,617, respectively)		4,487,172
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity warrants		0		0
Other derivative assets, Fair Value		0		0
Equity Securities, FV-NI		1		1
Servicing rights		0		0
Derivative liabilities		0		0
Debt Securities, Held-to-maturity, Fair Value		165,663
Securities available-for-sale, at fair value (amortized cost of $5,443,677 and $5,654,617, respectively)		664,202		670,070
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity warrants		0		0
Other derivative assets, Fair Value		8,463		7,814
Equity Securities, FV-NI		0		0
Servicing rights		0		0
Derivative liabilities		6,931		5,906
Debt Securities, Held-to-maturity, Fair Value		1,844,757		1,938,772
Securities available-for-sale, at fair value (amortized cost of $5,443,677 and $5,654,617, respectively)		3,820,606		4,173,417
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity warrants		3,807		4,048
Other derivative assets, Fair Value		0		0
Equity Securities, FV-NI		0		0
Servicing rights		701		633
Derivative liabilities		0		0
Debt Securities, Held-to-maturity, Fair Value		2,875		0
Securities available-for-sale, at fair value (amortized cost of $5,443,677 and $5,654,617, respectively)		2,364		0
NonPCI and PCI Loans | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net		0		0
NonPCI and PCI Loans | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net		$ 28,234		$ 28,065

[1] Excludes accrued interest receivable of $11.3 million at September 30, 2023 which is recorded in "Other assets" on the condensed consolidated balance sheets

[2] Excludes accrued interest receivable of $13.5 million at December 31, 2022 which is recorded in "Other assets" on the condensed consolidated balance sheets

[3] Excludes accrued interest receivable of $95.4 million and $124.3 million at September 30, 2023 and December 31, 2022, respectively, which is recorded in "Other assets" on the condensed consolidated balance sheets.