Summary of Significant Accounting Policies - Summary of Basic and Diluted Weighted Average Common Shares (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Basic weighted average common shares outstanding	17,919	17,984	17,927
Weighted average common equivalent shares	321	285	216
Diluted weighted average common shares outstanding	18,240	18,269	18,143
Options excluded from diluted weighted average share calculation as effect would have been anti-dilutive	133	706	1,237