Related Party Transactions - Related Party Transactions (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Gal-Tex Hotel Corporation | Mortgage loan on real estate
Related Party Transaction [Line Items]
Dollar Amount of Transactions	$ 576	$ 809
Gal-Tex Hotel Corporation | Net investment income
Related Party Transaction [Line Items]
Dollar Amount of Transactions	9	68
Gal-Tex Hotel Corporation | Mortgage loan on real estate
Related Party Transaction [Line Items]
Amount due to (from) American National	0		$ 576
Gal-Tex Hotel Corporation | Net investment income
Related Party Transaction [Line Items]
Amount due to (from) American National	0		3
Greer, Herz & Adams, LLP | Other operating expenses
Related Party Transaction [Line Items]
Dollar Amount of Transactions	5,896	$ 5,379
Greer, Herz & Adams, LLP | Other operating expenses
Related Party Transaction [Line Items]
Amount due to (from) American National	$ (494)		$ (329)