Summary of Significant Accounting Policies - Weighted-Average Common Stock Used to Calculate Basic and Diluted Earnings Per Share (Detail) - shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Weighted-average common stock for calculating basic earnings per share	23,927	23,911	23,900	23,862	23,932	25,334	26,142	26,091	23,900	25,369	25,914
Effect of potentially dilutive securities from equity-based compensation									76	88	261
Weighted-average common stock for calculating diluted earnings per share	24,123	24,041	23,949	23,911	24,015	25,408	26,273	26,276	23,976	25,457	26,175