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General (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract] |  |  |  |  |
Potentially dilutive securities (in shares) | 82,000 | 0 | 73,000 | 0 |
Deferred policy acquisition cost amortization | $ 142,295 | $ 136,290 | $ 424,799 | $ 416,728 |
Advertising expenses |  |  | 34,000 | 32,000 |
Revenue from contract with customer |  |  | 12,300 | 11,600 | $ 15,200
Related expenses from contracts with customers |  |  | $ 7,600 | $ 7,800 | $ 10,200
Disaggregation of Revenue [Line Items] |  |  |  |  |
Revenue from contract with customer, percentage of revenue |  |  | 0.50% | 0.50% | 0.40%
Commission income receivable | 1,100 |  | $ 1,100 |  | $ 1,200
Refund liability | $ 700 |  | $ 700 |  | $ 700
Insurance Policies [Member] | Auto Insurance Specialists LLC and Poliseek AIS Insurance Solutions Inc |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |
Revenue from contract with customer, percentage of revenue |  |  | 80.00% |  |

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