Subordinated Debentures - Narrative (Details)	6 Months Ended
Jun. 30, 2020 USD ($) note	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Aggregate principal amount of debt issued	$ 505,403,000
Subordinated debentures	501,375,000	$ 215,145,000
Subordinated notes
Debt Instrument [Line Items]
Aggregate principal amount of debt issued	495,000,000
Subordinated debentures	493,345,000	$ 207,187,000
FHLB advances and other borrowings	$ 3,600,000
Number of notes/securities \| note	5
Weighted interest rate	5.41%	5.37%
Subordinated notes \| Subordinated notes due 2026, 5.5% per annum until June 30 2021, 3-month LIBOR +4.285% thereafter
Debt Instrument [Line Items]
Aggregate principal amount of debt issued	$ 135,000,000
Fixed interest rate (as a percent)	5.50%
Subordinated debentures	$ 138,613,000	$ 0
Subordinated notes \| Subordinated notes due 2026, 5.5% per annum until June 30 2021, 3-month LIBOR +4.285% thereafter \| LIBOR
Debt Instrument [Line Items]
Floating interest rate, basis points added to base rate (as a percent)	4.285%
Subordinated notes \| Subordinated notes due 2030, 5.375% per annum until June 15, 2025, 3-month SOFR +5.17% thereafter
Debt Instrument [Line Items]
Aggregate principal amount of debt issued	$ 150,000,000.0
Fixed interest rate (as a percent)	5.375%
Subordinated debentures	$ 147,370,000	0
Offering price, percentage of aggregate principal amount	100.00%
Unamortized debt issuance cost	$ 2,300,000
Subordinated notes \| Subordinated notes due 2030, 5.375% per annum until June 15, 2025, 3-month SOFR +5.17% thereafter \| SOFR
Debt Instrument [Line Items]
Floating interest rate, basis points added to base rate (as a percent)	5.17%
Subordinated debt
Debt Instrument [Line Items]
Aggregate principal amount of debt issued	$ 10,403,000
Subordinated debentures	$ 8,030,000	$ 7,958,000
Number of notes/securities \| note	2

Debt Instrument, Number of Debt Instruments

No definition available.

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- Definition

Debt Instrument, Offering Price, Percentage of Face Amount

+ References

No definition available.

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- Definition

This element represents the amount of any measurement period adjustment (as defined) realized during the reporting period to financial liabilities assumed in connection with a business combination for which the initial accounting was incomplete.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 4A
-Subparagraph (c)
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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

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.

+ References

No definition available.

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- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

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- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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- Definition

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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-SubTopic 10
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