Fair Value Measurements - Qualitative Valuation (Details) $ in Thousands	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Measured on non-recurring basis
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Mortgage servicing rights	$ 774	$ 681
Loans measured for impairment based on the fair value of the underlying collateral	708	1,063
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	6,657,586	6,219,008
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	774	681
Loans measured for impairment based on the fair value of the underlying collateral	$ 708	$ 1,063
Significant Unobservable Inputs (Level 3) \| Discount Rate \| Measured on non-recurring basis \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired financing receivable, measurement input	0	0
Significant Unobservable Inputs (Level 3) \| Discount Rate \| Measured on non-recurring basis \| Weighted Average \| Estimated Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Impaired financing receivable, measurement input	0	0
Servicing asset, measurement input	0.1025	0.1175
Significant Unobservable Inputs (Level 3) \| Prepayment Speeds and Discounts Rates \| 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	0.089	0.036
Significant Unobservable Inputs (Level 3) \| Prepayment Speeds and Discounts Rates \| 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	0.277	0.240
Significant Unobservable Inputs (Level 3) \| Prepayment Speeds and Discounts Rates \| 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	0.183	0.127

Impaired Financing Receivable, Measurement Input

No definition available.

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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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- 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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- 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
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122492-111745

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-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

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

+ Details

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Balance Type:	debit
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- Definition

Value of input used to measure servicing asset.

+ 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

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