Stockholders' Equity (Common Stock) - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	Apr. 13, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 13, 2020	Dec. 31, 2018
Class of Stock [Line Items]
Stock repurchased and retired, total costs		$ 1,309	$ 1,005	$ 1,326	$ 1,023
Dividends per common share	$ 0.40
Dividends, date of record	May 15, 2020
Dividends. date of payable	Jun. 19, 2020
Share Repurchase Plan [Member]
Class of Stock [Line Items]
Common stock repurchase authorized amount						$ 20,000	$ 20,000
Common stock repurchased and retired, weighted average price, excluding fees and commissions		$ 40.48	$ 41.44	$ 39.92	$ 41.54
Stock repurchased and retired, total costs		$ 2,100	$ 6,668	$ 5,141	$ 8,006
Common stock repurchased and retired, weighted average price, including fees and commissions		$ 40.51	$ 41.47	$ 39.95	$ 41.57
Common Stock [Member]
Class of Stock [Line Items]
Repurchase and retirement of common stock, shares		29,102	24,478	29,473	24,849
Common Stock [Member] | Share Repurchase Plan [Member]
Class of Stock [Line Items]
Repurchase and retirement of common stock, shares		51,834	160,787	128,685	192,576