XML 54 R42.htm IDEA: XBRL DOCUMENT v3.8.0.1
Investments - Schedule of Components of Investment Income (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Oct. 31, 2017
Oct. 31, 2016
Oct. 31, 2017
Oct. 31, 2016
Investments, Debt and Equity Securities [Abstract]        
Interest income $ 10,038 $ 3,642 $ 24,433 $ 17,961
Realized gains 258 210 770 7,771
Realized losses (247) (143) (1,134) (1,985)
Total investment income $ 10,049 $ 3,709 $ 24,069 $ 23,747