Loans and Allowance for Credit Losses - Additional Information (Details)	12 Months Ended
Dec. 31, 2018 USD ($) TDR	Dec. 31, 2017 USD ($) TDR	Dec. 31, 2016 USD ($) TDR
Accounts Notes And Loans Receivable [Line Items]
Interest income recognized for impaired loans	$ 300,000	$ 1,600,000	$ 1,400,000
Contractual interest recognized on cash basis	$ 1,700,000	$ 1,500,000	$ 1,100,000
Number of TDRs experiencing payment default \| TDR		0	0
Number of TDRs \| TDR	6	6	9
ACI Loans
Accounts Notes And Loans Receivable [Line Items]
Number of TDRs experiencing payment default \| TDR	0	0	0
Number of TDRs \| TDR	0	0
Residential Real Estate
Accounts Notes And Loans Receivable [Line Items]
Foreclosed residential properties	$ 1,000,000	$ 2,700,000
Residential Real Estate \| Consumer Loans
Accounts Notes And Loans Receivable [Line Items]
Residential mortgage loans in process of foreclosure	3,800,000	$ 4,400,000
Consumer
Accounts Notes And Loans Receivable [Line Items]
Number of TDRs \| TDR		2	2
Consumer \| Residential Real Estate
Accounts Notes And Loans Receivable [Line Items]
Purchase of consumer residential real estate loans	$ 214,000,000
Premium percentage of consumer residential real estate loans	6.00%
Consumer \| Residential Real Estate \| ANCI Loans
Accounts Notes And Loans Receivable [Line Items]
Loans evaluated and determined credit impaired	$ 0

Financing receivable allowance for credit losses evaluated for impairment.

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- Definition

Carrying value of foreclosed residential real estate properties included in other real estate.

+ References

No definition available.

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- Definition

Premium percentage of consumer residential real estate loans.

+ References

No definition available.

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- Definition

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+ References

No definition available.

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- Definition

The amount of contractual interest expense on prepetition liabilities not included in the statement of operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84165509&loc=d3e56145-112766

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6918054&loc=d3e56068-112765

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524

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- Definition

The amount of interest income on impaired and nonperforming loans that is due to the change in present value attributable to the passage of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5278-111524

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- Definition

Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL49126937-111524

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- Definition

The cash outflow for the purchase of loan receivable arising from the financing of goods and services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

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