Fair Value Measurements - Qualitative Valuation (Details) $ in Thousands	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Measured on non-recurring basis
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Mortgage servicing rights	$ 582	$ 442
Loans measured for impairment based on the fair value of the underlying collateral		125
Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Loans measured for impairment based on the fair value of the underlying collateral	5,219,669	4,841,830
Significant Unobservable Inputs (Level 3) \| Measured on non-recurring basis
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Mortgage servicing rights	$ 582	442
Loans measured for impairment based on the fair value of the underlying collateral		$ 125
Significant Unobservable Inputs (Level 3) \| Discount Rate \| Measured on non-recurring basis \| Appraisal
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired financing receivable, measurement input		0.060
Significant Unobservable Inputs (Level 3) \| Discount Rate \| Measured on non-recurring basis \| Contract Sales Price
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other real estate owned, measurement input		0.060
Significant Unobservable Inputs (Level 3) \| Discount Rate \| Measured on non-recurring basis \| Weighted Average \| Appraisal
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired financing receivable, measurement input		0.060
Significant Unobservable Inputs (Level 3) \| Discount Rate \| Measured on non-recurring basis \| Weighted Average \| Contract Sales Price
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other real estate owned, measurement input		0.060
Significant Unobservable Inputs (Level 3) \| Prepayment Rate \| Measured on non-recurring basis \| Minimum \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Servicing asset, measurement input	0.058	0.033
Significant Unobservable Inputs (Level 3) \| Prepayment Rate \| Measured on non-recurring basis \| Maximum \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Servicing asset, measurement input	0.214	0.268
Significant Unobservable Inputs (Level 3) \| Prepayment Rate \| Measured on non-recurring basis \| Weighted Average \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Servicing asset, measurement input	0.130	0.120

Impaired Financing Receivable, Measurement Input

No definition available.

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Data Type:	xbrli:decimalItemType
Balance Type:	na
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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.

+ Details

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Period Type:	duration

- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Value of input used to measure real estate owned by financial institution by financial institution which is not directly related to its business.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122625-111746

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Value of input used to measure servicing asset.

+ References

+ Details

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Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Details

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- Details

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