Accumulated Other Comprehensive Income (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013
Interest expense
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (237,599)
Other comprehensive income before reclassification	569
Amount reclassified to mortgage-backed securities available for sale	(5,452)
Amounts reclassified to interest expense	29,929
Net current period other comprehensive income	25,046
Ending balance	(212,553)
Net gain on the sale of mortgage backed securities | Available-for-sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance accumulated other comprehensive income	499,343
Other comprehensive income before reclassification	(15,520)
Amounts reclassified to interest expense	(2,500)
Net current period other comprehensive income	(18,020)
Ending balance accumulated other comprehensive income	481,323
Net gain on the sale of mortgage backed securities | Unsettled Agency Contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance accumulated other comprehensive income	1,217
Other comprehensive income before reclassification	492
Amount reclassified to mortgage-backed securities available for sale	(1,217)
Net current period other comprehensive income	(725)
Ending balance accumulated other comprehensive income	492
Net gain on the sale of mortgage backed securities | Other Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance accumulated other comprehensive income	(107)
Other comprehensive income before reclassification	(107)
Net current period other comprehensive income	(107)
Ending balance accumulated other comprehensive income	$ (214)