Fair Value Measurements - Carrying Amounts and Estimated Fair Values of Certain Financial Instruments (Details) - USD ($) $ in Thousands		Jun. 30, 2022		Dec. 31, 2021	Jun. 30, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		$ 197,027		$ 112,548
Interest-earning deposits in financial institutions		2,192,877		3,944,686
Securities available-for-sale, Carrying Amount		6,780,648
Investment in FHLB stock, Carrying Amount		33,210		17,250
Investment in FHLB stock, Fair Value		33,210		17,250
Securities held-to-maturity, at amortized cost, net of allowance for credit losses		2,260,367	[1]	0
Loans and leases, net	[2]	26,312,432		22,740,984
Loans and leases held for investment, net		24,639,943
Warrants and Rights Outstanding				3,555
Other derivative assets, Carrying Amount		4,829		2,509	$ 4,001
Equity Securities, FV-NI		57		28,578
Servicing rights		839		1,228
Demand, interest checking, money market, and savings deposits		29,218,646		32,734,949
Interest-bearing Domestic Deposit, Brokered		2,185,248		889,976
Time deposits		2,564,258		1,372,832
Time deposits		2,542,229		1,371,527
Borrowings		1,592,000		0
Borrowings		1,591,920		0
Subordinated debt		863,756		863,283
Subordinated Debt Obligations, Fair Value Disclosure		880,648		917,342
Derivative Liability		4,008		931
Debt Securities, Held-to-maturity, Fair Value	[1]	2,209,759
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		197,027		112,548
Interest-earning deposits in financial institutions		2,192,877		3,944,686
Investment in FHLB stock, Fair Value		0		0
Demand, interest checking, money market, and savings deposits		0		0
Interest-bearing Domestic Deposit, Brokered		0		0
Time deposits		0		0
Borrowings		1,392,000		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		33,210		17,250
Demand, interest checking, money market, and savings deposits		29,218,646		32,734,949
Interest-bearing Domestic Deposit, Brokered		2,185,248		889,976
Time deposits		2,542,229		1,371,527
Borrowings		199,920		0
Subordinated Debt Obligations, Fair Value Disclosure		880,648		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 and leases held for investment, net		24,626,183
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		0		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		4,001		3,555
Other derivative assets, Fair Value		4,829		2,509
Derivative liabilities		4,008		931
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		57		28,578
Servicing rights		0		0
Derivative liabilities		0		0
Debt Securities, Held-to-maturity, Fair Value		180,896
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		4,829		2,509
Equity Securities, FV-NI		0		0
Servicing rights		0		0
Derivative liabilities		4,008		931
Debt Securities, Held-to-maturity, Fair Value		2,028,863
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity warrants		4,001		3,555
Other derivative assets, Fair Value		0		0
Equity Securities, FV-NI		0		0
Servicing rights		839		1,228
Derivative liabilities		0		0
Debt Securities, Held-to-maturity, Fair Value		0
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		$ 13,760		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 $13.7 million at June 30, 2022 which is recorded in "Other assets" on the condensed consolidated balance sheets

[2] Excludes accrued interest receivable of $88.9 million and $80.3 million at June 30, 2022 and December 31, 2021, respectively, which is recorded in "Other assets" on the condensed consolidated balance sheets.