XML 60 R47.htm IDEA: XBRL DOCUMENT v3.10.0.1
Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Schedule Of Accounting Policies [Line Items]        
Percentage of comparable consolidated amounts   95.00% 95.00% 95.00%
Provisional amounts an increase in the deferred tax balance   $ 1,500,000    
Original maturity of cash equivalent   90 days    
Experience rated commission and other operating costs   $ 200,000 $ 200,000  
Cash received, under reinsurance agreements     200,000  
Commutation payment adjusted through offset against balance of funds     25,400,000  
Advertising expense   $ 500,000 $ 500,000 $ 700,000
Assessment Related premium Payment period   1 year    
Assessment Related loss Payment period   1 year    
Buildings [Member]        
Schedule Of Accounting Policies [Line Items]        
Estimated useful life of assets   39 years    
Limited Partnership [Member]        
Schedule Of Accounting Policies [Line Items]        
Unfunded commitments   $ 0    
Minimum [Member]        
Schedule Of Accounting Policies [Line Items]        
Short-term investments maturity period   90 days    
Minimum [Member] | Other Fixed Assets [Member]        
Schedule Of Accounting Policies [Line Items]        
Estimated useful life of assets   3 years    
Maximum [Member]        
Schedule Of Accounting Policies [Line Items]        
Short-term investments maturity period   1 year    
Maximum [Member] | Other Fixed Assets [Member]        
Schedule Of Accounting Policies [Line Items]        
Estimated useful life of assets   7 years    
ASU 2016-01 [Member]        
Schedule Of Accounting Policies [Line Items]        
Decrease in net income $ 390,000      
ASU 2016-01 [Member] | Common Shares [Member]        
Schedule Of Accounting Policies [Line Items]        
Decrease to diluted earnings per common share $ 0.02