Investment Securities - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Amortized Cost And Fair Value Debt Securities [Abstract]
Proceeds From Sale of Investment			$ 24,031,000	$ 8,000
Gross Realized Gain from Sale of Investment	0	0	61,000	1,000
Unrealized Loss From Investment less than 12 months	901,145,000		901,145,000		2,995,000
Unrealized Loss From Investment More than 12 months	0		0		0
Investment Securities Pledged	$ 11,400,000		$ 11,400,000		$ 10,000,000