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Mortgage Servicing Rights - Summary of Retention and Purchase of MSRs (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Mortgage Servicing Rights [Line Items] |  |  |
MSR Fair Value | $ 7,387 | $ 10,060 | $ 64,725
MSRs |  |  |
Mortgage Servicing Rights [Line Items] |  |  |
MSR Fair Value | 8,026 | 25,362 | $ 95,281
Associated Principal | 792,371 | 2,926,572 |
MSRs | Jumbo Loans |  |  |
Mortgage Servicing Rights [Line Items] |  |  |
MSR Fair Value | 7,386 | 6,628 |
Associated Principal | 686,263 | 966,705 |
MSRs | Jumbo Loans | Securitizations |  |  |
Mortgage Servicing Rights [Line Items] |  |  |
MSR Fair Value | 7,123 | 6,451 |
Associated Principal | 654,605 | 939,861 |
MSRs | Jumbo Loans | Loan Sales |  |  |
Mortgage Servicing Rights [Line Items] |  |  |
MSR Fair Value | 263 | 177 |
Associated Principal | 31,658 | 26,844 |
MSRs | Conforming Loans |  |  |
Mortgage Servicing Rights [Line Items] |  |  |
MSR Fair Value | 640 | 18,734 |
Associated Principal | 106,108 | 1,959,867 |
MSRs | Conforming Loans | Loan Sales |  |  |
Mortgage Servicing Rights [Line Items] |  |  |
MSR Fair Value | 0 | 3,380 |
Associated Principal | 0 | 316,290 |
MSRs | Conforming Loans | Loan Purchases |  |  |
Mortgage Servicing Rights [Line Items] |  |  |
MSR Fair Value | 640 | 15,354 |
Associated Principal | $ 106,108 | $ 1,643,577 |

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- Definition Mortgage Servicing Rights [Line Items] + References No definition available. + Details
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- Definition Amount of additions from purchases, assumption or transfer to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 50 -Paragraph 4 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122739-111746 + Details
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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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 50 -Paragraph 3 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746 + Details
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