Fair Value Measurements (Details 8) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 185,075	$ 175,830
Interest-earning deposits in financial institutions	422,663	209,937
Securities available-for-sale, Carrying Amount	3,807,244	4,009,431
Investment in FHLB stock, Carrying Amount	43,146	32,103
Investment in FHLB stock, Fair Value	43,146	32,103
Loans and leases, net	18,337,815	17,825,241
Loans and leases held for investment, net	17,841,445
Warrants and Rights Outstanding		4,793
Other derivative assets, Carrying Amount	1,459	3,292
Equity Securities, FV-NI	3,284	4,891
Demand, interest checking, money market, and savings deposits	15,617,488	16,346,671
Interest-bearing Domestic Deposit, Brokered	436,833	518,192
Time deposits	2,751,435	2,005,638
Time deposits	2,749,828	2,017,137
Borrowings	1,913,059	1,371,114
Borrowings	1,913,059	1,371,114
Subordinated debentures	456,112	453,846
Subordinated debentures	439,635	435,251
Derivative Liability	317	142
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	185,075	175,830
Interest-earning deposits in financial institutions	422,663	209,937
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	1,903,000	1,371,000
Subordinated debentures	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	43,146	32,103
Demand, interest checking, money market, and savings deposits	15,617,488	16,346,671
Interest-bearing Domestic Deposit, Brokered	436,833	518,192
Time deposits	2,749,828	2,017,137
Borrowings	10,059	114
Subordinated debentures	439,635	435,251
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	17,841,445
Equity warrants		4,793
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 debentures	0	0
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity warrants	3,931	4,793
Other derivative assets, Fair Value	1,459	3,292
Derivative liabilities	317	142
Fair Value, Measurements, Recurring \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, Carrying Amount	5,188	403,405
Equity warrants	0	0
Other derivative assets, Fair Value	0	0
Equity Securities, FV-NI	3,284	4,891
Derivative liabilities	0	0
Fair Value, Measurements, Recurring \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, Carrying Amount	3,761,660	3,558,793
Equity warrants	0	0
Other derivative assets, Fair Value	1,459	3,292
Equity Securities, FV-NI	0	0
Derivative liabilities	317	142
Fair Value, Measurements, Recurring \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, Carrying Amount	40,396	47,233
Equity warrants	3,931	4,793
Other derivative assets, Fair Value	0	0
Equity Securities, FV-NI	0	0
Derivative liabilities	0	0
NonPCI and PCI Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net		17,013,860
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	$ 0	1,800
NonPCI and PCI Loans \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases held for investment, net		$ 17,012,060

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Securities Available For Sale Including Covered Securities

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Amount of interest bearing deposits with no stated maturity, which may include passbook and statement savings accounts and money-market deposit accounts (MMDAs).

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Fair value of securities received as collateral against derivative assets.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value of securities pledged as collateral against derivative liabilities.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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For banks and other depository institutions (including Federal Reserve Banks, if applicable): Interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet.

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Amount of interest-bearing domestic third-party deposits placed by or through the assistance of a deposit broker, also known as brokered deposit liabilities.

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Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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Amount of time deposit liabilities, including certificates of deposit.

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Value of outstanding derivative securities that permit the holder the right to purchase securities (usually equity) from the issuer at a specified price.

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Fair value portion of warrants not settleable in cash classified as equity.

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