Disclosures about Fair Value of Assets and Liabilities - Quantitative Information about Unobservable Inputs (Details)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Quantitative information about unobservable inputs
Mortgage servicing rights	$ 98,331,000	$ 82,604,000
Level 3 \| Mortgage servicing rights \| Single Family
Quantitative information about unobservable inputs
Mortgage servicing rights	$ 20,234,000	$ 9,035,000
Level 3 \| Mortgage servicing rights \| Single Family \| Discount Rate
Quantitative information about unobservable inputs
Servicing asset, measurement input		0.11
Level 3 \| Mortgage servicing rights \| Single Family \| Discount Rate \| Weighted average
Quantitative information about unobservable inputs
Servicing asset, measurement input		0.11
Level 3 \| Mortgage servicing rights \| Single Family \| Constant Prepayment Rate \| Minimum
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.11	0.08
Level 3 \| Mortgage servicing rights \| Single Family \| Constant Prepayment Rate \| Maximum
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.14	0.35
Level 3 \| Mortgage servicing rights \| Single Family \| Constant Prepayment Rate \| Weighted average
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.12
Level 3 \| Mortgage servicing rights \| Single Family \| Mortgage Yield \| Minimum
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.09
Level 3 \| Mortgage servicing rights \| Single Family \| Mortgage Yield \| Maximum
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.10
Level 3 \| Mortgage servicing rights \| Single Family \| Mortgage Yield \| Weighted average
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.09
Level 3 \| Mortgage servicing rights \| Multi-family
Quantitative information about unobservable inputs
Mortgage servicing rights	$ 78,097,000	$ 73,569,000
Level 3 \| Mortgage servicing rights \| Multi-family \| Discount Rate \| Minimum
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.08	0.08
Level 3 \| Mortgage servicing rights \| Multi-family \| Discount Rate \| Maximum
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.13	0.13
Level 3 \| Mortgage servicing rights \| Multi-family \| Discount Rate \| Weighted average
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.09	0.09
Level 3 \| Mortgage servicing rights \| Multi-family \| Constant Prepayment Rate \| Minimum
Quantitative information about unobservable inputs
Servicing asset, measurement input	0	0.02
Level 3 \| Mortgage servicing rights \| Multi-family \| Constant Prepayment Rate \| Maximum
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.43	0.43
Level 3 \| Mortgage servicing rights \| Multi-family \| Constant Prepayment Rate \| Weighted average
Quantitative information about unobservable inputs
Servicing asset, measurement input	0.03	0.04
Level 3 \| Collateral-dependent impaired loans
Quantitative information about unobservable inputs
Collateral-dependent impaired loans	$ 3,807,000	$ 4,059,000
Marketability discount (as a percent)	0.49	0.43
Level 3 \| Collateral-dependent impaired loans \| Minimum
Quantitative information about unobservable inputs
Marketability discount (as a percent)		0.43
Level 3 \| Collateral-dependent impaired loans \| Weighted average
Quantitative information about unobservable inputs
Marketability discount (as a percent)	0.49	0.43
Level 3 \| Interest Rate Lock Commitments
Quantitative information about unobservable inputs
Derivative assets	$ 487,000	$ 6,131,000
Derivative liabilities	$ 54,000
Level 3 \| Interest Rate Lock Commitments \| Measurement Input, Maturity \| Minimum
Quantitative information about unobservable inputs
Loan closing rates (as a percent)	0.63	0.55
Loan closing rates (as a percent)	0.63
Level 3 \| Interest Rate Lock Commitments \| Measurement Input, Maturity \| Maximum
Quantitative information about unobservable inputs
Loan closing rates (as a percent)	0.99	0.99
Loan closing rates (as a percent)	0.99
Level 3 \| Interest Rate Lock Commitments \| Measurement Input, Maturity \| Weighted average
Quantitative information about unobservable inputs
Loan closing rates (as a percent)	0.82	0.75
Loan closing rates (as a percent)	0.82

The fair value amount of impaired loans.

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Value of input used to measure collateral-dependent impaired loans.

+ References

No definition available.

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Value of input used to measure derivative 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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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Value of input used to measure derivative liability.

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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

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
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Value of input used to measure servicing asset.

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