• Filing Date: 2017-02-22
  • Form Type: 10-K
  • Description: Annual report
v3.6.0.2
Investments (Net Investment Income) - Additional Information (Detail)
$ in Thousands
Dec. 31, 2016
USD ($)
Accounts
Bank
Dec. 31, 2015
USD ($)
Accounts
Bank
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Schedule of Investments [Line Items]        
Cash and cash equivalents $ 280,531 $ 267,738 $ 314,416 $ 293,098
Deposits representing cash and cash equivalents in percentage 72.60% 56.00%    
Number of national banks | Bank 3 3    
Number of custodial accounts | Accounts 3 3    
Federal Deposit Insurance Corporation's coverage limit for insured deposit accounts $ 250 $ 250    
Custodial Accounts [Member]        
Schedule of Investments [Line Items]        
Cash and cash equivalents 28,431 65,291    
Bank Deposits [Member]        
Schedule of Investments [Line Items]        
Cash and cash equivalents $ 203,139 $ 150,048