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Reinsurance - Narrative (Details) - USD ($) |  | 1 Months Ended | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Jul. 01, 2015 | Mar. 31, 2017 | Sep. 30, 2015 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |
Ceded premiums written, net of profit commission |  |  |  | $ 133,885,000 | $ 55,391,000 | $ 119,634,000 |
Ceded to Other Companies |  |  |  | 133,981,000 | 102,848,000 | 108,255,000 |
Less reinsurance recoverable |  |  |  | $ 50,493,000 | $ 44,487,000 | 57,841,000 | $ 64,085,000
Period of existing captive reinsurance agreement |  |  |  | 10 years | 10 years |  |
Reinsurance recoverable on loss reserves related to captive agreements |  |  |  | $ 19,000,000 | $ 34,000,000 |  |
Fair value of trust fund assets under our captive agreements |  |  |  | 91,000,000 | 137,000,000 |  |
Quota Share Reinsurance Agreement, 2015 |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |
Contingent termination fee | $ 0 |  |  |  |  |  |
Threshold for private mortgage insurer eligibility requirements for termination election | 90.00% |  |  |  |  |  |
Quota share, percentage | 30.00% |  |  |  |  |  |
Ceding commission, percentage | 20.00% |  |  |  |  |  |
Loss ratio | 60.00% |  |  |  |  |  |
Ceded premiums written, net of profit commission |  |  |  | 125,460,000 | 52,588,000 |  |
Ceded to Other Companies |  |  |  | 125,460,000 | 52,588,000 |  |
Ceding commission |  |  |  | 47,629,000 | 20,582,000 |  |
Profit commission |  |  |  | 112,685,000 | 50,322,000 |  |
Less reinsurance recoverable |  |  |  | $ 31,800,000 | 10,900,000 |  |
Quota Share Reinsurance Agreement, 2013 |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |
Ceded premiums written, net of profit commission |  |  | $ 69,400,000 |  | (11,355,000) | 100,031,000 |
Ceded to Other Companies |  |  | 11,600,000 |  | 35,999,000 | 88,528,000 |
Ceding commission |  |  | $ 11,600,000 |  | 10,235,000 | 37,833,000 |
Profit commission | $ 142,500,000 |  |  |  | $ 62,525,000 | $ 89,133,000 |
Quota Share Reinsurance Agreement, 2017 | Forecast |  |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |  |
Contingent termination fee |  | $ 0 |  |  |  |  |
Threshold for private mortgage insurer eligibility requirements for termination election |  | 90.00% |  |  |  |  |
Quota share, percentage |  | 30.00% |  |  |  |  |
Ceding commission, percentage |  | 20.00% |  |  |  |  |
Loss ratio |  | 60.00% |  |  |  |  |

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- Definition The known and estimated amount recoverable, related to captive agreements, as of the balance sheet date from reinsurers for claims paid or incurred by the ceding insurer and associated claims settlement expenses, including estimated amounts for claims incurred but not reported, and policy benefits, net of any related valuation allowance. + References No definition available. + Details
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- Definition Amount of earned premiums ceded to other entities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6486662&loc=d3e27175-158546 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915 + Details
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- Definition Amount of written premiums ceded to other entities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12 + Details
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