Summary of Significant Accounting Policies - Shares Used in Computation of Basic and Diluted Per Share Information (Detail)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Weighted Average Shares Outstanding:
Weighted average number of shares outstanding for basic per share calculation	17,274,677	17,260,078	17,233,264	17,148,043	17,096,360	17,083,201	17,055,619	16,966,525	17,229,026	17,049,794	17,853,321
Effect of dilutive potential shares:
Options									4,284	4,058	1,909
Nonvested Stock Awards									82,023	78,899	43,965
Weighted Average Number of Shares Outstanding, Diluted (shares)	17,419,423	17,356,916	17,277,224	17,268,716	17,228,499	17,182,013	17,127,017	17,073,543	17,315,333	17,132,751	17,899,195
Antidilutive shares									173,360	182,225	345,122