Subordinated Debt and Other borrowings - Narrative (Details)	9 Months Ended
Sep. 30, 2018 USD ($) subsidiary	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Number of wholly owned subsidiaries \| subsidiary	12
Term	30 years
Subordinated debt and other borrowings \| $	$ 465,487,000	$ 465,505,000
Variable rate basis description	LIBOR + 3.128%
BNC Bancorp \| BNC Subordinated Notes Assumed Due October 2023 \| Minimum
Debt Instrument [Line Items]
Interest rate (as percent)	5.50%
BNC Bancorp \| BNC Subordinated Notes Assumed Due October 2023 \| Maximum
Debt Instrument [Line Items]
Interest rate (as percent)	9.50%

Number of wholly owned subsidiaries.

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- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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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

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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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.

+ References

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