Summary of Significant Accounting Policies - Weighted Average Shares and Share Equivalents Used to Calculate Basic and Diluted Earnings Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Weighted average number of shares outstanding used to calculate basic EPS (in Shares)	3,733	3,847	4,022
Dilutive securities:
Stock options and restricted share units (in Shares)	507	257	233
Weighted average number of shares and share equivalents outstanding used to calculate diluted EPS (in Shares)	4,240	4,104	4,255