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Financial Guarantee Liability - Additional Information (Detail) - USD ($) $ in Billions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Dec. 31, 2017
Credit Risk [Member] | Fannie Mae and Freddie Mac [Member] |  |
Guarantee Obligations [Line Items] |  |
Outstanding principal balances of credit risk loans being serviced | $ 18.9 | $ 18.8
Maximum potential loss of credit risk loans being serviced | 5.4 | 5.3
Credit Risk [Member] | Fannie Mae and Freddie Mac [Member] | Credit Enhancement Agreement [Member] |  |
Guarantee Obligations [Line Items] |  |
Maximum potential loss of credit risk loans being serviced | $ 0.1 | $ 1.2
Fannie Mae DUS or Freddie TAH Loans [Member] | Maximum [Member] |  |
Guarantee Obligations [Line Items] |  |
Percentage of contingent liability of actual losses incurred on outstanding loans | 33.00% |

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- Definition For entities that provide full or partial financing and servicing for customers supplementary to its major operations (such as a manufacturer or a homebuilder providing and servicing loans to buyers), represents the liabilities associated with such activities, including accounts payable and accrued liabilities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.15) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.15) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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