Loans, Purchase Credit Impaired ("PCI") Loans (Details) - TCSB Bancorp, Inc. [Member] - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Carrying amount of loans that meet the criteria of ASC 310-30 treatment [Abstract]
Total carrying amount	$ 2,332		$ 2,332		$ 2,513
Allowance for loan losses	0		0		0
Carrying amount, net of allowance for loan losses	2,332		2,332		2,513
Accretable yield of PCI loans, or income expected to be collected [Roll Forward]
Balance at beginning of period	749	$ 533	462	$ 0
New loans purchased	0	0	0	568
Accretion recorded as loan interest income	(56)	(32)	(134)	(67)
Reclassification from (to) nonaccretable difference	0	0	365	0
Disposals/other adjustments	0	0	0	0
Balance at end of period	693	$ 501	693	$ 501
Commercial [Member]
Carrying amount of loans that meet the criteria of ASC 310-30 treatment [Abstract]
Total carrying amount	1,421		1,421		1,609
Mortgage [Member]
Carrying amount of loans that meet the criteria of ASC 310-30 treatment [Abstract]
Total carrying amount	582		582		555
Installment [Member]
Carrying amount of loans that meet the criteria of ASC 310-30 treatment [Abstract]
Total carrying amount	$ 329		$ 329		$ 349

Amount of the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118938799&loc=d3e13503-111538

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 50
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-Subparagraph (a)(2)
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Amount of accretion recognized for the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities, with evidence of deterioration of credit quality.

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Amount of additions to the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

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Amount of reduction, resulting from a sale or transfer of a loan, in the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of reclassification (to) from nonaccretable difference (from) to the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

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Reserve for loans impairments recorded after acquisition as a result of current information and events which result in it being probable that estimated cash flows will be less than previously expected or because actual cash flows are less than cash flows previously expected. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

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The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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- Definition

The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

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