Company's Invested Assets and Derivative Instruments Measured at Fair Value on Recurring Basis (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investment in limited partnership	$ 66,121	$ 32,592