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Mortgage Banking Activities, Mortgage Servicing Rights (Details) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2019 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2019 USD ($) | Sep. 30, 2018 USD ($) | Dec. 31, 2018 USD ($)
Summary of Mortgage Servicing Rights [Abstract] |  |  |  |  |
Number of residential mortgage loans serviced for others | 128,463 |  | 128,463 |  | 132,463
Outstanding principal balance of residential mortgage loans serviced for others | $ 21,046,136,000 |  | $ 21,046,136,000 |  | $ 21,658,335,000
Weighted average interest rate | 3.99% |  | 3.99% |  | 3.99%
Remaining term (in months) |  |  | 290 months |  | 293 months
Servicing Asset at Fair Value, Amount [Roll Forward] |  |  |  |  |
Beginning balance | $ 208,308,000 | $ 278,719,000 | $ 259,254,000 | $ 252,867,000 | $ 252,867,000
Additions, net | 9,882,000 | 8,968,000 | 24,821,000 | 28,688,000 |
Change in fair value due to principal payments | (11,936,000) | (8,986,000) | (27,600,000) | (25,783,000) |
Change in fair value due to market assumption changes | (12,593,000) | 5,972,000 | (62,814,000) | 28,901,000 |
Ending balance | $ 193,661,000 | $ 284,673,000 | $ 193,661,000 | $ 284,673,000 | $ 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) |  |  | 9.82% |  | 9.90%
Prepayment rate - based upon loan interest rate, original term and loan type, minimum |  |  | 8.31% |  | 8.05%
Prepayment rate - based upon loan interest rate, original term and loan type, maximum |  |  | 17.22% |  | 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
Escrow earnings rate - indexed to rates paid on deposit accounts with comparable average life (in hundredths) |  |  | 1.51% |  | 2.57%
Primary secondary mortgage rate spread | 102 |  | 102 |  | 105

X
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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 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 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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