Fair Value Measurements (Details 7) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 233,215	$ 337,965
Interest-earning deposits in financial institutions	165,222	81,705
Securities available-for-sale, at fair value		3,223,830
Securities available-for-sale, at fair value	3,774,431	3,223,830
Federal Home Loan Bank stock, at cost	20,790	21,870
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	20,790	21,870
Cost Method Investments	977	1,416
Cost Method Investments, Fair Value Disclosure	9,573	3,843
Loans and leases, net	16,833,287	15,298,716
Loans Receivable, Fair Value Disclosure	17,023,098
Warrants and Rights Outstanding		5,497
Derivative Asset	1,873	694
Warrants Not Settleable in Cash, Fair Value Disclosure		5,497
Deposits, Savings Deposits	15,937,012	12,523,834
Interest-bearing Domestic Deposit, Brokered	863,202	1,174,487
Time Deposits	2,065,322	2,172,290
Deposits, Fair Value Disclosure	2,055,104	2,166,187
Borrowings	467,342	905,812
Long-term Debt, Fair Value	467,343	905,838
Subordinated debentures	462,437	440,744
Subordinated Debt Obligations, Fair Value Disclosure	444,383	424,507
Derivative Liability		3,285
Loans held for sale, at lower of cost or fair value	481,100	0
Loans Held-for-sale, Fair Value Disclosure	483,563
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	233,215	337,965
Interest-earning deposits in financial institutions	165,222	81,705
Securities available-for-sale, at fair value		2,080
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	0	0
Cost Method Investments, Fair Value Disclosure	0	0
Deposits, Savings Deposits	0	0
Interest-bearing Domestic Deposit, Brokered	0	0
Deposits, Fair Value Disclosure	0	0
Long-term Debt, Fair Value	467,000	591,000
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
Securities available-for-sale, at fair value		3,156,475
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	20,790	21,870
Cost Method Investments, Fair Value Disclosure	0	0
Deposits, Savings Deposits	15,937,012	12,523,834
Interest-bearing Domestic Deposit, Brokered	863,202	1,174,487
Deposits, Fair Value Disclosure	2,055,104	2,166,187
Long-term Debt, Fair Value	343	314,838
Subordinated Debt Obligations, Fair Value Disclosure	444,383	424,507
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
Securities available-for-sale, at fair value		65,275
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	0	0
Cost Method Investments, Fair Value Disclosure	9,573	3,843
Loans Receivable, Fair Value Disclosure	17,017,955
Warrants Not Settleable in Cash, Fair Value Disclosure		5,497	$ 4,914
Deposits, Savings Deposits	0	0
Interest-bearing Domestic Deposit, Brokered	0	0
Deposits, Fair Value Disclosure	0	0
Long-term Debt, Fair Value	0	0
Subordinated Debt Obligations, Fair Value Disclosure	0	0
NonPCI and PCI Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases, net		15,298,716
Loans Receivable, Fair Value Disclosure		15,494,808
NonPCI and PCI Loans [Member] \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable, Fair Value Disclosure		0
NonPCI and PCI Loans [Member] \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable, Fair Value Disclosure		1,661
NonPCI and PCI Loans [Member] \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable, Fair Value Disclosure		15,493,147
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	3,774,431	3,223,830
Derivative Asset, Fair Value of Collateral	1,873	694
Warrants Not Settleable in Cash, Fair Value Disclosure	5,161	5,497
Derivative Liability, Fair Value of Collateral	1,379	3,285
Fair Value, Measurements, Recurring [Member] \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	5,922	2,080
Derivative Asset, Fair Value of Collateral	0	0
Warrants Not Settleable in Cash, Fair Value Disclosure	0	0
Derivative Liability, Fair Value of Collateral	0	0
Fair Value, Measurements, Recurring [Member] \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	3,703,526	3,156,475
Derivative Asset, Fair Value of Collateral	1,873	694
Warrants Not Settleable in Cash, Fair Value Disclosure	0	0
Derivative Liability, Fair Value of Collateral	1,379	3,285
Fair Value, Measurements, Recurring [Member] \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available-for-sale, at fair value	64,983	65,275
Derivative Asset, Fair Value of Collateral	0	0
Warrants Not Settleable in Cash, Fair Value Disclosure	5,161	5,497
Derivative Liability, Fair Value of Collateral	0	$ 0
Non Purchased Credit Impaired Loans and Leases [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Held-for-sale, Fair Value Disclosure	0
Non Purchased Credit Impaired Loans and Leases [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Held-for-sale, Fair Value Disclosure	483,563
Non Purchased Credit Impaired Loans and Leases [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Held-for-sale, Fair Value Disclosure	$ 0

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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Amount, after adjustment, of cost-method investment. Adjustments include, but are not limited to, dividends received in excess of earnings after date of investment that are considered a return of investment and other than temporary impairments.

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Fair value portion of investments accounted under the cost method.

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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, after the effects of master netting arrangements, of a financial liability or 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 liabilities 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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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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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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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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