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Mortgage Banking Activities, Mortgage Servicing Rights (Details) | 12 Months Ended
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Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Summary of Mortgage Servicing Rights [Abstract] |  |  |
Number of residential mortgage loans serviced for others | 126,828 | 132,463 | 136,528
Outstanding principal balance of residential mortgage loans serviced for others | $ 20,727,106,000 | $ 21,658,335,000 | $ 22,046,632,000
Weighted average interest rate (in hundredths) | 3.98% | 3.99% | 3.94%
Remaining contractual term (in months) | 289 months | 293 months | 297 months
Servicing Asset at Fair Value, Amount [Roll Forward] |  |  |
Beginning balance | $ 259,254,000 | $ 252,867,000 | $ 247,073,000
Additions, net | 35,128,000 | 35,247,000 | 39,149,000
Change in fair value due to loan runoff | (38,979,000) | (33,528,000) | (33,527,000)
Change in fair value due to market changes | (53,517,000) | 4,668,000 | 172,000
Ending balance | $ 201,886,000 | $ 259,254,000 | $ 252,867,000
Servicing Assets at Fair Value, Assumptions Used to Estimate Fair Value [Abstract] |  |  |
Discount rate - risk-free rate plus a market premium (in hundredths) | 9.81% | 9.90% |
Prepayment rate - based upon loan interest rate, original term and loan type, minimum | 8.28% | 8.05% |
Prepayment rate - based upon loan interest rate, original term and loan type, maximum | 16.05% | 15.74% |
Loan servicing costs - annually per loan based upon loan type, performing, minimum (in dollars per loan) | $ 68 | $ 67 |
Loan servicing costs - annually per loan based upon loan type, performing, maximum (in dollars per loan) | 94 | 93 |
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) | 104 | 105 |
Escrow earnings rate - indexed to rates paid on deposit accounts with comparable average life | 1.73% | 2.57% |
Delinquency rate | 2.73% | 2.74% |

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- Definition Indicates the number of mortgage loans being serviced. + References No definition available. + Details
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- Definition Servicing Assets at Fair Value Assumptions Used to Estimate Fair Value Delinquent Loan Service Cost Minimum + References No definition available. + Details
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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. + References No definition available. + Details
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- Definition Servicing Assets At Fair Value Assumptions Used to Estimate Fair Value Foreclosure Loan Service Cost Maximum + References No definition available. + Details
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- Definition Servicing Assets at Fair Value Assumptions Used to Estimate Fair Value Foreclosure Loan Service Cost Minimum + References No definition available. + Details
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- Definition The maximum cost to service a performing loan for the period used as a variable in estimating fair value. + References No definition available. + Details
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- Definition The minimum cost to service a performing loan for the period used as a variable in estimating fair value. + References No definition available. + Details
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- Definition 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. + References No definition available. + Details
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- Definition 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. + References No definition available. + Details
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- Definition Represents the weighted average interest rate of loans servicedf for others as of the balance sheet date. + References No definition available. + Details
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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. + References No definition available. + 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 -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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