Stockholders' Equity - Restricted Stock Vested by or Granted to Non-Executive Directors (Detail) (USD $)	3 Months Ended												39 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2014
Equity [Abstract]
Price Per Share	$ 13.01	$ 15.4	$ 18.17	$ 14.28	$ 14.16	$ 13.57	$ 13.27	$ 11.68	$ 11.87	$ 12.86	$ 13.93	$ 13.87
Restricted Stock Granted	7,110	6,006	5,093	6,475	6,266	4,606	4,712	5,350	5,263	4,084	3,769	3,785	62,519
Restricted Stock Vested	0	0	0	0	(6,266)	(4,606)	(4,712)	(5,350)	(5,263)	(4,084)	(3,769)	(3,785)	(37,835)
Restricted Stock Granted and Outstanding	7,110	6,006	5,093	6,475	0	0	0	0	0	0	0	0	24,684
Cash Dividends Paid					$ 3,133	$ 1,935	$ 1,979	$ 2,247	$ 2,211	$ 2,042	$ 2,356	$ 2,839	$ 18,742