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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Weighted-average common stock for calculating basic earnings per share	23,932	25,334	26,142	26,091	25,999	25,953	25,912	25,789	25,369	25,914	25,433
Effect of potentially dilutive securities from equity-based compensation									88	261	493
Weighted-average common stock for calculating diluted earnings per share	24,015	25,408	26,273	26,276	26,206	26,152	26,220	26,230	25,457	26,175	25,926