Changes in Accumulated Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012	Jun. 30, 2013 Net Unrealized Gains (Losses) on Securities [Member]	Jun. 30, 2012 Net Unrealized Gains (Losses) on Securities [Member]	Jun. 30, 2013 Net Unrealized Gains (Losses) on Securities [Member]	Jun. 30, 2012 Net Unrealized Gains (Losses) on Securities [Member]	Jun. 30, 2013 Pension and Postretirement Benefit Plans [Member]	Mar. 31, 2013 Pension and Postretirement Benefit Plans [Member]	Dec. 31, 2012 Pension and Postretirement Benefit Plans [Member]	Jun. 30, 2012 Pension and Postretirement Benefit Plans [Member]	Mar. 31, 2012 Pension and Postretirement Benefit Plans [Member]	Dec. 31, 2011 Pension and Postretirement Benefit Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	$ (431,284)	$ 367,888	$ (380,726)	[1]	$ 445,339	$ 228,637	$ 683,279	$ 279,195	$ 760,730	$ (659,921)	$ (659,921)	$ (659,921)	$ (315,391)	$ (315,391)	$ (315,391)
Change in net unrealized holding gains on securities, before reclassifications, net of tax benefit	(820,336)	214,107	(789,753)		142,505	(820,336)	214,107	(868,953)	142,505
Reclassification for previously unrealized net (gains) and impairments on securities recognized in net income, net of tax	(97,530)	(326,010)	(178,671)		(331,859)	(97,530)	(326,010)	(99,471)	(331,859)
Ending balance	$ (1,349,150)	$ 255,985	$ (1,349,150)		$ 255,985	$ (689,229)	$ 571,376	$ (689,229)	$ 571,376	$ (659,921)	$ (659,921)	$ (659,921)	$ (315,391)	$ (315,391)	$ (315,391)

[1] Derived from the audited consolidated financial statements.