XML 59 R50.htm IDEA: XBRL DOCUMENT v3.8.0.1
Investments - Gross Realized Gains and Losses on Sale of Securities (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Investments Debt And Equity Securities [Abstract]        
Gross realized gains $ 1,094 $ 1,346 $ 3,324 $ 5,226
Gross realized losses $ (85) $ (30) $ (455) $ (1,072)