Other Comprehensive Income (Loss) - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Amounts Reclassified Out Of Accumulated Other Comprehensive Income Loss [Abstract]
Reclassification of gains or (losses) and impairment charges on sales of securities	$ 328,000	$ 0	$ 362,000	$ 2,578,000
Other than temporary impairment of securities available for sale	0	0	0	0
Disproportional tax effects in accumulated other comprehensive income (loss)			$ (16,600,000)