Effect of Reinsurance on Premiums Written and Earned (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded written premiums	$ 94,905	[1]	$ 88,989	[1]	$ 18,072
Ceded earned premiums	96,552	[1]	92,852	[1]	$ 18,547
American Bankers Insurance Company
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded written premiums	35,300		55,800
Ceded earned premiums	$ 43,200		$ 59,500

[1] Includes ceded written premiums and ceded earned premiums of $55.8 million and $59.5 million, respectively, to American Bankers Insurance Company.