Summary of Significant Accounting Policies - Shares Used in Computation of Basic and Diluted Per Share Information (Detail) - shares	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
Weighted Average Shares Outstanding:
Weighted average number of shares outstanding for basic per share calculation	17,447,691	17,436,731	17,410,971	17,322,791	17,274,677	17,260,078	17,233,264	17,148,043	17,405,379	17,229,026	17,049,794
Effect of dilutive potential shares:
Options									3,663	4,284	4,058
Nonvested Stock Awards									138,488	82,023	78,899
Weighted Average Number of Shares Outstanding, Diluted (shares)	17,647,483	17,610,953	17,529,100	17,489,483	17,419,423	17,356,916	17,277,224	17,268,716	17,547,531	17,315,333	17,132,751
Antidilutive shares									200,525	173,360	182,225