Liability for Unpaid Claims and Claim Adjustment Expenses - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Insurance [Abstract]
Description of increase (decrease) in claims and claim adjustment expenses	The net and gross reserve calculations have shown favorable development as a result of favorable loss emergence compared to what was implied by the loss development patterns used in the original estimation of losses in prior years.
Decrease in claims and claim adjustments expenses amount	$ 19,852	$ 77,296	$ 36,788
Short-duration health insurance claims	$ 39,337
Percentage of IBNR reserves applied to paid adjusting and other expense to paid loss	100.00%