• Filing Date: 2018-03-07
  • Form Type: 10-K
  • Description: Annual report
v3.8.0.1
Investments - Summary of Securities with Gross Unrealized Loss Positions Aggregated by Investment Category (Detail) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Loss, Less than Twelve Months $ (1,102) $ (2,510)
Fair Value, Less than Twelve Months 106,282 86,896
Gross Unrealized Loss, Twelve Months or Longer (869) (379)
Fair Value, Twelve Months or Longer 36,274 11,013
Gross Unrealized Loss, Total (1,971) (2,889)
Fair Value, Total 142,556 97,909
Equity Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Loss, Less than Twelve Months (449) (293)
Fair Value, Less than Twelve Months 12,812 10,042
Gross Unrealized Loss, Twelve Months or Longer (52) (191)
Fair Value, Twelve Months or Longer 1,440 3,209
Gross Unrealized Loss, Total (501) (484)
Fair Value, Total 14,252 13,251
Fixed-Maturity Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Loss, Less than Twelve Months (653) (2,217)
Fair Value, Less than Twelve Months 93,470 76,854
Gross Unrealized Loss, Twelve Months or Longer (817) (188)
Fair Value, Twelve Months or Longer 34,834 7,804
Gross Unrealized Loss, Total (1,470) (2,405)
Fair Value, Total 128,304 84,658
Fixed-Maturity Securities [Member] | U.S. Treasury and U.S. Government Agencies [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Loss, Less than Twelve Months (246) (36)
Fair Value, Less than Twelve Months 40,587 1,939
Gross Unrealized Loss, Twelve Months or Longer (41)  
Fair Value, Twelve Months or Longer 1,938  
Gross Unrealized Loss, Total (287) (36)
Fair Value, Total 42,525 1,939
Fixed-Maturity Securities [Member] | Corporate Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Loss, Less than Twelve Months (174) (1,546)
Fair Value, Less than Twelve Months 40,627 43,859
Gross Unrealized Loss, Twelve Months or Longer (730) (95)
Fair Value, Twelve Months or Longer 30,563 2,814
Gross Unrealized Loss, Total (904) (1,641)
Fair Value, Total 71,190 46,673
Fixed-Maturity Securities [Member] | State, Municipalities, and Political Subdivisions [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Loss, Less than Twelve Months (30) (441)
Fair Value, Less than Twelve Months 9,775 26,029
Gross Unrealized Loss, Twelve Months or Longer (45) (47)
Fair Value, Twelve Months or Longer 2,297 3,036
Gross Unrealized Loss, Total (75) (488)
Fair Value, Total 12,072 29,065
Fixed-Maturity Securities [Member] | Exchange-Traded Debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Loss, Less than Twelve Months (203) (191)
Fair Value, Less than Twelve Months 2,481 4,980
Gross Unrealized Loss, Twelve Months or Longer (1) (46)
Fair Value, Twelve Months or Longer 36 1,954
Gross Unrealized Loss, Total (204) (237)
Fair Value, Total $ 2,517 6,934
Fixed-Maturity Securities [Member] | Redeemable Preferred Stock [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Loss, Less than Twelve Months   (3)
Fair Value, Less than Twelve Months   47
Gross Unrealized Loss, Total   (3)
Fair Value, Total   $ 47