Components of Investment Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Interest income	$ 1,928	$ 629	$ 400
Realized gains, net	0	0	2
Total	$ 1,928	$ 629	$ 402