Fair Value Disclosures - Estimated Fair Value of Company's Financial Assets and Financial Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Financial assets:
Cash and cash equivalents, Fair Value	$ 282,409	$ 134,129
Securities - Held to maturity, Fair value	8,094	7,527
Loans not previously presented Fair Value	3,432,384	2,800,362
Loans included in assets held for sale, net, Fair Value		69,268
Accrued interest receivable, Fair Value	20,141	15,517
Cash and cash equivalents, Carrying Amount	282,409	134,129	$ 80,557	$ 114,514
Securities - held to maturity, Carrying Amount	8,403	8,557
Loans not previously presented Carrying Amount	3,494,184	2,780,228
Loans included in assets held for sale, net, Carrying Amount		68,668
FHLB stock, Carrying Amount	23,109	16,006
Accrued interest receivable, Carrying Amount	20,141	15,517
Financial liabilities:
Deposits, Fair Value	3,428,722	2,616,034
Customer repurchase agreements, Fair Value	13,248	11,488
Federal Home Loan Bank advances, Fair Value	330,000	365,000
Subordinated notes, Fair Value	51,125	52,310
Junior subordinated debentures, Fair Value	41,057	41,563
Accrued interest payable, Fair Value	6,072	3,323
Deposits, Carrying Amount	3,439,049	2,621,348
Customer repurchase agreements, Carrying Amount	13,248	11,488
Federal Home Loan Bank advances, Carrying Amount	330,000	365,000
Subordinated notes, Carrying Amount	48,903	48,828
Junior subordinated debentures, Carrying Amount	38,966	38,623
Accrued interest payable, Carrying Amount	6,072	3,323
Level 1
Financial assets:
Cash and cash equivalents, Fair Value	282,409	134,129
Accrued interest receivable, Fair Value	20,141	15,517
Financial liabilities:
Accrued interest payable, Fair Value	6,072	3,323
Level 2
Financial liabilities:
Deposits, Fair Value	3,428,722	2,616,034
Customer repurchase agreements, Fair Value	13,248	11,488
Federal Home Loan Bank advances, Fair Value	330,000	365,000
Subordinated notes, Fair Value	51,125	52,310
Junior subordinated debentures, Fair Value	41,057	41,563
Level 3
Financial assets:
Securities - Held to maturity, Fair value	8,094	7,527
Loans not previously presented Fair Value	$ 3,432,384	2,800,362
Loans included in assets held for sale, net, Fair Value		$ 69,268

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Accrued interest receivable fair value disclosure.

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Junior subordinated notes fair value disclosure.

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Loans and leases receivable net reported amount included in assets held for sale.

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Loans and leases receivable reported amount not previously presented.

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Loans included in assets held for sale fair value disclosure.

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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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Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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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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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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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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Amount of investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of interest payable on debt, including, but not limited to, trade payables.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

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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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Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.

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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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