Summary of Information Regarding Repurchases of Common Stock (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended						12 Months Ended
	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Common Stock Repurchases [Abstract]
Number of Shares	3,900	22,811	88,445	9,800	59,006	214,087	183,962
Weighted average per share purchase price	$ 9.47	$ 9.45	$ 9.24	$ 5.87	$ 5.60	$ 4.67	$ 7.94
Total purchase price	$ 37	$ 216	$ 817	$ 58	$ 332	$ 1,000	$ 1,070	$ 58	$ 1,332
Amount remaining for repurchase	$ 2,540	$ 2,577	$ 793	$ 1,610	$ 1,668		$ 2,540		$ 1,668