Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Certain Financial Instruments (Details) - USD ($) $ in Thousands		Mar. 31, 2023		Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		$ 218,830		$ 212,273
Interest-earning deposits in financial institutions		6,461,306		2,027,949
Securities available-for-sale, Carrying Amount		4,848,607		4,843,487
Investment in FHLB stock, Carrying Amount		147,150		34,290
Investment in FHLB stock, Fair Value		147,150		34,290
Loans Held-for-sale, Fair Value Disclosure		2,807,699		65,501
Loans Receivable Held-for-sale, Amount		2,796,208		65,076
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss		2,273,650	[1]	2,269,135	[2]
Loans and leases, net	[3]	25,462,326		28,408,397
Loans and leases held for investment, net		24,138,162		26,627,985
Equity Securities, FV-NI		1		1
Servicing rights		1,409		633
Demand, interest checking, money market, and savings deposits		19,230,293		26,561,129
Interest-bearing Domestic Deposit, Brokered		2,028,676		2,637,362
Time deposits		6,928,592		4,737,843
Time deposits		6,945,479		4,700,054
Borrowings (including $128,375 at fair value)		11,881,712		1,764,030
Borrowings		11,899,375		1,764,037
Subordinated debt		868,815		867,087
Subordinated Debt Obligations, Fair Value Disclosure		823,002		870,534
Derivative Liability		5,178		5,906
Debt Securities, Held-to-maturity, Fair Value		2,157,056	[1]	2,110,472	[2]
Securities available-for-sale, at fair value (amortized cost of $5,591,766 and $5,654,617, respectively)		4,848,607		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		184,862		184,162
Debt Securities, Held-to-maturity, Fair Value		176,629		171,700
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		218,830		212,273
Interest-earning deposits in financial institutions		6,461,306		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
Interest-bearing Domestic Deposit, Brokered		0		0
Time deposits		0		0
Borrowings		4,910,000		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		147,150		34,290
Loans Held-for-sale, Fair Value Disclosure		2,807,699		65,501
Demand, interest checking, money market, and savings deposits		19,230,293		26,561,129
Interest-bearing Domestic Deposit, Brokered		2,028,676		2,637,362
Time deposits		6,945,479		4,700,054
Borrowings		5,450,000		750,007
Subordinated Debt Obligations, Fair Value Disclosure		823,002		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		24,115,010		26,599,920
Equity warrants				4,048
Demand, interest checking, money market, and savings deposits		0		0
Interest-bearing Domestic Deposit, Brokered		0		0
Time deposits		0		0
Borrowings		1,539,375		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		3,978		4,048
Other derivative assets, Fair Value		7,025		7,814
Derivative liabilities		5,178		5,906
Securities available-for-sale, at fair value (amortized cost of $5,591,766 and $5,654,617, respectively)		4,848,607
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		176,629
Securities available-for-sale, at fair value (amortized cost of $5,591,766 and $5,654,617, respectively)		685,436		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		7,025		7,814
Equity Securities, FV-NI		0		0
Servicing rights		0		0
Derivative liabilities		5,178		5,906
Debt Securities, Held-to-maturity, Fair Value		1,945,900		1,938,772
Securities available-for-sale, at fair value (amortized cost of $5,591,766 and $5,654,617, respectively)		4,148,392		4,173,417
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity warrants		3,978		4,048
Other derivative assets, Fair Value		0		0
Equity Securities, FV-NI		0		0
Servicing rights		1,409		633
Derivative liabilities		0		0
Debt Securities, Held-to-maturity, Fair Value		34,527		0
Securities available-for-sale, at fair value (amortized cost of $5,591,766 and $5,654,617, respectively)		14,779		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		$ 23,152		$ 28,065

[1] Excludes accrued interest receivable of $11.3 million at March 31, 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 $131.7 million and $124.3 million at March 31, 2023 and December 31, 2022, respectively, which is recorded in "Other assets" on the condensed consolidated balance sheets.