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Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Unrecorded Unconditional Purchase Obligation |  |  |
Operating leases, rent expense | $ 2.5 | $ 1.9 | $ 2.7
Construction Contracts |  |  |
Unrecorded Unconditional Purchase Obligation |  |  |
Commitments under construction contracts | $ 1.1 |  |
Related Entity |  |  |
Unrecorded Unconditional Purchase Obligation |  |  |
Ownership percentage in partnership | 50.00% |  |
Obligation to repurchase loans sold |  |  |
Unrecorded Unconditional Purchase Obligation |  |  |
Amount of sold residential mortgage loans with recourse provisions | $ 1.9 | $ 2.7 |

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- Definition Reflects the estimated amount of loss from the specified contingency as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349 + Details
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- Definition Amount of the unrecorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 440 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=77896938&loc=d3e25336-109308 + Details
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