Insurance Activity - Schedule of Premiums Assumed and Earned (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Insurance [Abstract]
Premiums assumed	$ 2,656	$ 4,788	$ 6,869
Change in unearned premiums	491	333	300
Premiums earned	$ 3,147	$ 5,121	$ 7,169