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Reinsurance - Summary of Reinsurance Agreements (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
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Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Premiums Earned, Net [Abstract] |  |  |  |  |  |  |  |  |  |  |
Premiums earned, direct |  |  |  |  |  |  |  |  | $ 1,059,973 | $ 1,058,545 | $ 997,892
Premiums earned, assumed |  |  |  |  |  |  |  |  | 509 | 662 | 1,178
Premiums earned, ceded |  |  |  |  |  |  |  |  | (125,735) | (133,981) | (102,848)
Net premiums earned | $ 237,425 | $ 237,083 | $ 231,136 | $ 229,103 | $ 235,053 | $ 237,376 | $ 231,456 | $ 221,341 | 934,747 | 925,226 | 896,222
Policyholder Benefits and Claims Incurred, Net [Abstract] |  |  |  |  |  |  |  |  |  |  |
Losses incurred, direct |  |  |  |  |  |  |  |  | 74,727 | 273,207 | 369,680
Losses incurred, assumed |  |  |  |  |  |  |  |  | 183 | 1,138 | 1,552
Losses incurred, ceded |  |  |  |  |  |  |  |  | (21,201) | (34,188) | (27,685)
Net losses incurred | $ (30,996) | $ 29,747 | $ 27,339 | $ 27,619 | $ 47,658 | $ 60,897 | $ 46,590 | $ 85,012 | 53,709 | 240,157 | 343,547
Ceded premiums written, net of profit commission |  |  |  |  |  |  |  |  | 125,726 | 133,885 | 55,391
Ceded premiums earned, net of profit commission (1) |  |  |  |  |  |  |  |  | 125,735 | 133,981 | 102,848
Ceded losses incurred |  |  |  |  |  |  |  |  | 21,201 | 34,188 | 27,685
Quota Share Reinsurance Agreements, Excluding Captives |  |  |  |  |  |  |  |  |  |  |
Premiums Earned, Net [Abstract] |  |  |  |  |  |  |  |  |  |  |
Premiums earned, ceded |  |  |  |  |  |  |  |  | (120,974) | (125,460) | (88,587)
Policyholder Benefits and Claims Incurred, Net [Abstract] |  |  |  |  |  |  |  |  |  |  |
Losses incurred, ceded |  |  |  |  |  |  |  |  | (22,336) | (30,201) | (17,484)
Ceded premiums written, net of profit commission |  |  |  |  |  |  |  |  | 120,974 | 125,460 | 41,233
Ceded premiums earned, net of profit commission (1) |  |  |  |  |  |  |  |  | 120,974 | 125,460 | 88,587
Ceded losses incurred |  |  |  |  |  |  |  |  | 22,336 | 30,201 | 17,484
Ceding commissions |  |  |  |  |  |  |  |  | 49,321 | 47,629 | 30,816
Profit commission |  |  |  |  |  |  |  |  | $ 125,629 | $ 112,685 | $ 112,847

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- Definition Amount of earned premiums assumed from other entities. + References Reference 1: 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 Reference 2: 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 3: 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 + 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=84167274&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 (c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 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)(3) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
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- Definition Amount of fees and commissions from financial services and banking activities and correspondent clearing. Includes fees from depositor accounts, credit cards, merchant discounts, and fiduciary and trust activities, guarantee fees, investment advisory, management, and administrative fees, transfer agent fees, and insurance commissions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.13) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition Amount, after effect of policies assumed or ceded, of expense related to provision for policy benefits and costs incurred for property and casualty insurance contracts. + 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 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 + Details
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- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of property and casualty premiums earned. + 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) -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=84167274&loc=d3e27175-158546 + Details
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