Mortgage Banking Activities, Mortgage Servicing Rights (Details)	12 Months Ended
Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Summary of Mortgage Servicing Rights [Abstract]
Number of residential mortgage loans serviced for others	106,201	126,828	132,463
Outstanding principal balance of residential mortgage loans serviced for others	$ 16,228,449,000	$ 20,727,106,000	$ 21,658,335,000
Weighted average interest rate (in hundredths)	3.84%	3.98%	3.99%
Remaining contractual term (in months)	280	289	293
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	$ 201,886,000	$ 259,254,000	$ 252,867,000
Additions, net	31,209,000	35,128,000	35,247,000
Disposals	(10,801,000)
Change in fair value due to loan runoff	(41,598,000)	(38,979,000)	(33,528,000)
Change in fair value due to market changes	(79,524,000)	(53,517,000)	4,668,000
Ending balance	$ 101,172,000	$ 201,886,000	$ 259,254,000
Servicing Assets at Fair Value, Assumptions Used to Estimate Fair Value [Abstract]
Discount rate - risk-free rate plus a market premium (in hundredths)	9.14%	9.81%
Prepayment rate - based upon loan interest rate, original term and loan type, minimum	9.41%	8.28%
Prepayment rate - based upon loan interest rate, original term and loan type, maximum	21.87%	16.05%
Loan servicing costs - annually per loan based upon loan type, performing, minimum (in dollars per loan)	$ 69	$ 68
Loan servicing costs - annually per loan based upon loan type, performing, maximum (in dollars per loan)	94	94
Loan servicing costs - annually per loan based upon loan type, delinquent, minimum (in dollars per loan)	150	150
Loan servicing costs - annually per loan based upon loan type, delinquent, maximum (in dollars per loan)	500	500
Loan servicing costs - annually per loan based upon loan type, foreclosure, minimum (in dollars per loan)	1,000	1,000
Loan servicing costs - annually per loan based upon loan type, foreclosure, maximum (in dollars per loan)	$ 4,000	$ 4,000
Primary secondary mortgage rate spread (in basis points)	105	104
Escrow earnings rate - indexed to rates paid on deposit accounts with comparable average life	0.43%	1.73%
Delinquency rate	3.54%	2.73%

The decrease in fair value as a result of loan runoff.

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- Definition

Mortgage rate spread between the primary and secondary market.

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Indicates the number of mortgage loans being serviced.

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Dollar amount of principal outstanding on mortgage loans being serviced.

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Represents the weighted average remaining term of mortgage loans being serviced fro others.

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Servicing Assets at Fair Value Assumptions Used to Estimate Fair Value Delinquent Loan Service Cost Minimum

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No definition available.

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Servicing Assets At Fair Value Assumptions Used to Estimate Fair Value Delinquent

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- Definition

The escrow earning rate used to estimate the fair value of servicing assets, based on rates paid on deposit accounts.

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- Definition

Servicing Assets At Fair Value Assumptions Used to Estimate Fair Value Foreclosure Loan Service Cost Maximum

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Servicing Assets at Fair Value Assumptions Used to Estimate Fair Value Foreclosure Loan Service Cost Minimum

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- Definition

The maximum cost to service a performing loan for the period used as a variable in estimating fair value.

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No definition available.

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The minimum cost to service a performing loan for the period used as a variable in estimating fair value.

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The maximum estimated speed of prepayments of principal on financial assets which may be one of the factors applied in estimating the fair value of servicing assets.

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The minimum estimated speed of prepayments of principal on financial assets which may be one of the factors applied in estimating the fair value of servicing assets.

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- Definition

Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Delinquency Rate

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- Definition

-- None. No documentation exists for this element. --

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- Definition

Represents the weighted average interest rate of loans servicedf for others as of the balance sheet date.

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No definition available.

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- Definition

Amount of increase (decrease) in fair value from changes in the assumptions or model used to calculate the fair value of a contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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No definition available.

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- Definition

The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122625-111746

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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
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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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Decrease in servicing assets subsequently measured at fair value resulting from conveyance of servicing rights to unrelated parties.

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Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

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