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Mortgage Servicing Rights, Net - Additional Information (Detail) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2019 | Dec. 31, 2018
Mortgage Servicing Rights [Line Items] |  |
Primary servicing portfolio | $ 58,100.0 | $ 57,100.0
Special servicing portfolio | $ 2,700.0 | $ 2,900.0
Minimum [Member] |  |
Mortgage Servicing Rights [Line Items] |  |
Discount rate | 3.00% | 3.00%
Maximum [Member] |  |
Mortgage Servicing Rights [Line Items] |  |
Discount rate | 13.50% | 13.50%
Discount Rate One [Member] |  |
Mortgage Servicing Rights [Line Items] |  |
Increase in discount rate | 1.00% | 1.00%
Decrease in fair value of servicing rights | $ (11.7) | $ (12.4)
Discount Rate Two [Member] |  |
Mortgage Servicing Rights [Line Items] |  |
Increase in discount rate | 2.00% | 2.00%
Decrease in fair value of servicing rights | $ (22.8) | $ (24.4)
Mortgage Servicing Rights [Member] |  |
Mortgage Servicing Rights [Line Items] |  |
Estimated fair value of MSRs | $ 431.5 | $ 451.9

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- Definition Percentage of increase in discount rate of servicing rights. + References No definition available. + Details
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- Definition Special servicing portfolio. + 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=68078379&loc=d3e122625-111746 + Details
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- Definition The increase (decrease) in the fair value of servicing assets that are subsequently measured at fair value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746 + Details
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- Definition Discount rate used to estimate the fair value of servicing assets and servicing liabilities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122596-111746 + Details
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