Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Certain Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2022		Dec. 31, 2021	Sep. 30, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		$ 216,436		$ 112,548
Interest-earning deposits in financial institutions		2,244,272		3,944,686
Securities available-for-sale, Carrying Amount		5,891,328
Investment in FHLB stock, Carrying Amount		36,990		17,250
Investment in FHLB stock, Fair Value		36,990		17,250
Loans Held-for-sale, Fair Value Disclosure		16,407
Loans Receivable Held-for-sale, Amount		15,534		0
Securities held-to-maturity, at amortized cost, net of allowance for credit losses		2,264,601	[1]	0
Loans and leases, net	[2]	27,470,714		22,740,984
Loans and leases held for investment, net		25,527,716
Warrants and Rights Outstanding				3,555
Other derivative assets, Carrying Amount		6,149		2,509	$ 4,215
Equity Securities, FV-NI		2		28,578
Servicing rights		712		1,228
Demand, interest checking, money market, and savings deposits		28,559,310		32,734,949
Interest-bearing Domestic Deposit, Brokered		2,367,544		889,976
Time deposits		3,269,018		1,372,832
Time deposits		3,232,022		1,371,527
Borrowings (including 132,815 at fair value)		1,864,815		0
Borrowings		1,864,815		0
Subordinated debt		863,379		863,283
Subordinated Debt Obligations, Fair Value Disclosure		807,820		917,342
Derivative Liability		6,367		931
Debt Securities, Held-to-maturity, Fair Value	[1]	2,060,846
Securities available-for-sale, at fair value		5,891,328		10,694,458
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		216,436		112,548
Interest-earning deposits in financial institutions		2,244,272		3,944,686
Investment in FHLB stock, Fair Value		0		0
Loans Held-for-sale, Fair Value Disclosure		0
Demand, interest checking, money market, and savings deposits		0		0
Interest-bearing Domestic Deposit, Brokered		0		0
Time deposits		0		0
Borrowings		1,732,000		0
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		36,990		17,250
Loans Held-for-sale, Fair Value Disclosure		16,407
Demand, interest checking, money market, and savings deposits		28,559,310		32,734,949
Interest-bearing Domestic Deposit, Brokered		2,367,544		889,976
Time deposits		3,232,022		1,371,527
Borrowings		0		0
Subordinated Debt Obligations, Fair Value Disclosure		807,820		917,342
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
Loans and leases held for investment, net		25,501,383
Equity warrants				3,555
Demand, interest checking, money market, and savings deposits		0		0
Interest-bearing Domestic Deposit, Brokered		0		0
Time deposits		0		0
Borrowings		132,815		0
Subordinated Debt Obligations, Fair Value Disclosure		0		0
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity warrants		4,215		3,555
Other derivative assets, Fair Value		6,149		2,509
Derivative liabilities		6,367		931
Securities available-for-sale, at fair value		5,891,328
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		2		28,578
Servicing rights		0		0
Derivative liabilities		0		0
Debt Securities, Held-to-maturity, Fair Value		170,010
Securities available-for-sale, at fair value		663,389		966,898
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		6,149		2,509
Equity Securities, FV-NI		0		0
Servicing rights		0		0
Derivative liabilities		6,367		931
Debt Securities, Held-to-maturity, Fair Value		1,890,836
Securities available-for-sale, at fair value		5,227,939		9,712,559
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity warrants		4,215		3,555
Other derivative assets, Fair Value		0		0
Equity Securities, FV-NI		0		0
Servicing rights		712		1,228
Derivative liabilities		0		0
Debt Securities, Held-to-maturity, Fair Value		0
Securities available-for-sale, at fair value		0		15,001
NonPCI and PCI Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net				23,461,156
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		$ 26,333		2,915
NonPCI and PCI Loans | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net				$ 23,458,241

[1] Excludes accrued interest receivable of $11.3 million at September 30, 2022 which is recorded in "Other assets" on the condensed consolidated balance sheets

[2] Excludes accrued interest receivable of $106.1 million and $80.3 million at September 30, 2022 and December 31, 2021, respectively, which is recorded in "Other assets" on the condensed consolidated balance sheets.