Schedule I - Dividends from Subsidiary - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Dividends Payable [Line Items]
Dividends payable	$ 84	$ 470
Stock repurchased during period, total cost	98,032
Dividends paid to stockholders	325	1,544	$ 65,306
Parent Company [Member]
Dividends Payable [Line Items]
Dividends payable	84	470
Stock repurchased during period, total cost	98,000
Dividends paid to stockholders	$ 325	$ 1,544	$ 65,306